I'm a federal retiree with a TSP account. The F fund is an index fund based on the Bloomberg Barclays Aggregate Bond Index. IIRC, the duration is around 4.5. The 8.65 1 year return reflects capital gains from falling interest rates, similar to the gains recorded by core bond funds/intermediate bond funds.

https://www.washingtonpost.com/business/2020/06/30/stocks-interest-rate-fed/
How the Fed is driving savers to riskier investments
The Federal Reserve’s efforts to buoy the economy and stabilize financial markets are working nicely for now — but we are in for a bumpy ride

American Funds’ Quiet Rise to Bond Dominance
https://www.barrons.com/articles/american-funds-quiet-rise-to-bond-dominance-51593714454
Incognito
https://www.google.com/search?q=American+Funds’+Quiet+Rise+to+Bond+Dominance&oq=American+Funds’+Quiet+Rise+to+Bond+Dominance&aqs=chrome..69i57j69i60l2.1043j0j7&sourceid=chrome-mobile&ie=UTF-8
While most investors have been laser-focused on stocks this year, the relative steadiness of the bond market has gone largely ignored. American Funds’ bond portfolios, however, have produced a remarkable amount of good news. Managed by Capital Group, they turned in top-notch performance during the coronavirus rout, and have steadily climbed to the pinnacle of their categories over longer periods.
The gains reflect a quiet overhaul that has transformed Capital Group, founded in 1931, into a bond giant.

VTI "The fund has returned 7.12% since its inception in 2001 (as of May 2020).)
FWIW, Derf

Forget earnings season. What’s the rest of 2020 going to look like?
https://www.marketwatch.com/story/forget-earnings-season-whats-the-rest-of-2020-going-to-look-like-2020-07-04?mod=markets
Investors will return from a long holiday weekend in the U.S. on Monday to what may be the calm before the storm: a relatively quiet week before a deluge of second-quarter corporate earnings reports are published starting July 13.
Most observers are looking past second quarter earnings, as they are likely to not only be awful, but to come without any useful guidance from companies on what to expect for the rest of the year. The bigger question, then, is: what’s next?

https://www.fedsmith.com/2020/07/01/which-tsp-fund-up-8-65-12-months/
Which TSP Fund Up 8.65% in 12 Months?
For those who casually watch the rate of return for the funds in the Thrift Savings Plan (TSP), this may be a surprise.
F Fund Has Best Return Over 12 Months

https://www.thinkadvisor.com/2020/07/02/how-optimistic-should-we-be-on-u-s-economy/
How Optimistic Should We Be on U.S. Economy?
By Jeff Berman |
The U.S. economy is pretty much a mixed bag right now amid spikes in new reported new COVID-19 cases in some states, according to Gary Cohn, former director of the National Economic Council and President Donald Trump’s former chief economic advisor, and Glenn Hutchins, co-founder of Silver Lake Partners.

Thanks for catching my mix-up on dates (the portfolio visualizer can start as far back as 1985 but not this portfolio).
I typically follow EDV but that only went back to 2009 so I looked at VEDTX instead which also includes 2008.
Those other combinations are impressive.
By using WHOSX instead you can get results back to 1998 as well.
Then I looked at different percentages with WHOSX.
PV results
It looks to me that you still need a significant amount of long-term treasuries to make any real difference.
Even WHOSX/PRMTX 50/50 still beats PRWCX.
PV results
Though the bottom line is, I don't think I could put 70% of my total portfolio in long-term treasuries and then just forget about it.

everyone saw this, right? (forgive if repost)
https://www.nytimes.com/2020/07/03/opinion/stock-market.html

Why aren't long-term treasuries utilized more (or actually at all) in actively managed multi-sector, unconstrained, or flexible income funds? I understand the volatility of such funds but it seems that they do add value. I got to thinking about this again after looking at the prospectus for TMSRX. I believe that they would characterize this under "Style Premia" strategy which includes currency bets (as of 4/20/20 they had 1.4% total in US treasuries).
Portfolio Visualizer for:
1) VEDTX & VTSMX (70/30)
2) VEDTX & QQQ (70/30)
3) PRWCX (100)
Dating back to 1985 (admittedly a period of decreasing interest rates):
Portfolio Visualizer results
Maximum drawdown 1 yr for:
1) -17.05
2) -9.25
3) -27.17
Final balance for a $10,000 investment would be:
1) $37,914
2) $48,708
3) $29,711
I've been following such a strategy for quite some time but never had the nerve to actually invest as such. PRWCX is my largest holding & have been very satisfied.

NYT: Deutsche Bank May Offer Wirecard a Lifeline
https://www.nytimes.com/2020/07/02/business/wirecard-deutsche-bank.html
Once again, Deutsche Bank puts on its not-so-white hat to cut a deal with a debt-ridden, likely fraudulent company that was headed by a questionable CEO. (Wirecard's former CEO is currently under arrest.)
"It did not provide any further details."

No one knows how long QE Infinity might endure. Biden is proposing a fiscal policy alternative to Cimmamond's MCD solution that could help to offset some of QE Infinity's destructive and destabilizing effects.

Seen in its full breadth and scope, the Biden tax plan is a progressive tour de force. Biden would fund his poverty-fighting education, housing, retirement and health-care reforms with $4.3 trillion of tax hikes on the rich.
Biden’s proposals are populist in the true sense of the term. The Tax Policy Center has found that three-quarters of his tax increases fall on the richest 1% of households. In 2021, Biden would raise this group’s taxes by $299,000.

https://marketwatch.com/story/liberals-arent-giving-joe-biden-credit-for-a-radical-tax-plan-that-goes-after-the-indolent-rich-2020-07-02

There may be less here than meets the eye.
For example, consider the highlighted sentence: "A greater proportion of American companies are older, larger, and more profitable than in the late 20th century, which explains much of the increase in corporate payouts."
Except that this isn't a report on American companies, but rather "nonfinancial firms listed on US exchanges that the researchers studied."
As is well known, the number of listed companies has declined by half since the 20th century. Naturally those remaining would tend to be the older, larger ones. Younger, smaller ones would be the ones choosing to stay private.
Vanguard has a nice paper discussing this in more depth:
What's behind the falling number of public companies? https://personal.vanguard.com/pdf/ISGPCA.pdf
The paragraph you reference doesn't hang together for me:

• The researchers did not find any evidence that higher payouts had reduced corporate capital expenditures or corporate performance; and
  
• While ... capital expenditures [of firms with high payouts] fell after 2000, the same was true for firms with lower payouts.

The second sentence says that the relative level of payouts across companies does not correlate with companies' capital expenditures. That's not the same as failing to find any relationship between higher payouts and lower capital expenditures.
The paper makes clear that since 2000 payouts have been increasing (that's the whole subject of the piece), and the second sentence says that all firms (on average) whether they're relatively high payers or not are reducing capital expenditures.
I take that as little more than the cost of capital declines as the US evolves toward an information based economy with cheap computers, storage, and networks.

July 2020 MFO Commentary is up. Nothing follows.

Thanks for the suggestion. Certainly the CMBS portion of the portfolio is one of the most likely candidates.
Almost all the CMBS holdings are derivatives and I really didn't want to get into estimating their yields. So I started with the assumption that within CMBSs, yields would tend to be similar. Thus I looked at the more basic securities.
My source of prices was the annual report that valued the securities as of March 31, ISTM any bargain basement purchases in March were already priced in. For example, there's a non-agency CMBS, BBCMS Mort. Trust, Series 2020-C6, Class F5TB 3.69%. (In the BBCMS Mort. Trust prospectus, it's Class F5T-B.) With principal of $75K, its current value (March 31) is given as $46,675.
Fund Annual Report
BBCMS Mort. Trust Prospectus
This security represents a mortgage on a single property, F5 Tower in Seattle (built 2019, 100% occupied), with an anticipated repayment date of January 6, 2030 (final maturity in 2033).

The prospectus gives the average weighted life as 9.91 years (about 119 months). The security was issued in mid February. That's close enough to the March 31 date of the fund's annual statement not to worry about the difference in dates.
The annual statement gives the principal amount as $75K and the current value as $46,675. With this information (and the info in the SEC filing) I could approximate the yield going forward.
To figure out the monthly payments received (principal and interest) I used an amortization calculator, and 119 months. (Outstanding principal doesn't change enough in the month from Feb to the March annual report date to worry about adjusting this.)
$75K principal, 3.69% average weighted rate (per SEC filing) gives monthly payments of about $754.
Since the fund valued the holding at $46,675, the question becomes: what would the rate be on a $46,675 mortgage (119 months) to require payments of $754? The answer is about 15%.
That's in line with the fund's yield. Good, but not enough to compensate for the lower yielding securities held by the fund, let alone its large cash position. The bottom line is that I still agree that the CMBS derivatives are a good place to search for the higher yielding securities.

The IRS has indicated that the first and second quarterly estimated tax payments for 2020 may be combined into one single payment due by July 15, 2020:
https://www.irs.gov/newsroom/irs-july-15-tax-payment-deadline-approaching-plan-on-scheduling-multiple-payments-now#:~:text=Taxpayers who owe a 2019,combined into a single payment.

I'm reviving this thread to ask the community their feeling about 2020 CG & Div distribution estimates compared to 2019. Higher - Lower - Same? The July 15 deadline for 1st and 2nd quarterly estimated tax payments is approaching and I'd like to be in the ballpark. I have Vanguard, FIDO, and TRP, but no specific sector concentration. The market looks a lot different now than it did back in March.

I haven't examined the fund too closely, but if you are looking for the reason for the returns and the potential liquidity risks, I would suggest considering the commercial mortgage backed securities CMBS exposure. They came under a lot of pressure recently, but I imagine if a manger timed the purchases right he/she could also make some attractive gains very quickly with them too. Not for the faint of heart most likely.

Inflation-indexed bonds fill an important gap in the fixed income market. Regular Treasury bonds are riskier than they seem – long-term Treasuries fell 60% in inflation-adjusted terms between 1940 and 1981. Minimizing duration is not a solution since real rates for short-term Treasuries have been as low as -9%. TIPS solve these issues by offering a safe bond investment not vulnerable to inflation.

5 Part Series:
Part 1:
history-of-tips-and-how-tips-bonds-work/
Part 2: How to Hedge Inflation and Avoid the Biggest Bond Risk
how-to-hedge-inflation-and-avoid-the-biggest-bond-risk/
Part 3: The Largest Arbitrage Ever Documented – TIPS in 2008
the-largest-arbitrage-ever-documented-tips-in-2008/
Part 4: Debunking TIPS Tax Inefficiency + A Tax Deferred Alternative
/debunking-tips-tax-inefficiency-a-tax-deferred-alternative/
Part 5: When TIPS Outperform and How I Invest in Them
when-tips-outperform-and-how-i-invest-in-them/

BigTom, I do see this fund as aggressive for a bond holding, but I think there is room for aggressive bond funds within an overall portfolio, especially when managers like Scott Minerd are saying stocks are priced for perfection but there is still value in certain sectors of fixed income.

That's correct. It depends on your style, age and goals. I use mostly bond funds and doing pretty good.
In the biggest meltdown in the last 10 years, MWFSX peak to trough was about 6%, VCIF was about 13%, BND (US bond index) all investment grade was about 6.5%. It shows that MWFSX managers did a great job. Is it a guarantee? of course not.
BTW, the Portfolio Composition(Characteristics,Sector Weight,Credit Quality,Duration Maturity) for MWFSX is as of 5/31/2020 based on real data. See (link).
Another observation, the monthly yield keeps getting smaller in the last 5 months.
So, only you can make this decision after gathering all the information.