Or doe these DSCR loans even mirror treasuries at all? 

Invest in a treasury.

You can invest excess cash flow and get 5% return (online savings, CDs, treasuries) (or simply pay down principal). 

Equity REITs (not mortgage REITS) are truly great though and have returned 1.5-2.0% more than SP500 over last 20/25/50 years in multiple retrospective studies, and are a great value purchase right now due to being beaten down by fast FED rate rise last 2 yrs, however to get best tax benefits, buy them only within a tax advantaged account like 401k/IRA etc as the big dividends are taxed very high at earned income rates.Good luck, wishing you and wife all the best on your investing journey :)               ps don't ever keep cash at a bank, park in your brokerage account and buy USFR, a wisdom tree ETF, pays 5.39% interest, holds only 8 week US treasury floating rate notes, so you don't need to worry about FDIC or SPIC insurance as only way US govt doesn't pay is if we get nuked, then you won't much care about cash yields, just non-radioactive water. 

I'm not an expert at this but something is off to me has anybody been told this as well.Thank you,Could be that the lender wants to avoid IRS/Treasury disclosure trouble for transactions over $10,000 (part of the know your customer rule).So as another poster said; when you say “cash” do you mean physical notes that we all carry around in our wallets? 

for some reason REITs have never been a sexy asset class, older investors look at REITs as a weird-bond and wonder why own something with 4-5% dividend when they can own Investment Grade corporates at 5-6% or even recently US treasuries at 5%, and young investors don't even know what they are.yet they acquire class A real estate, the kind you and I can't due to price, the kind that has the best capital appreciation in great areas long term, and they have access to credit at lower rates than us, or they can just print shares and get new capital for free that way, to buy more great properties, They can pay for the best management, they don't ever pay brokerage fees either in or out (have everything in -house), and they generally have much lower risk as most of their portfolios are leveraged at only about 30-40% LTV, and we have zero personal liability when owning them as opposed to the litigation headaches we get with direct RE, and right now they collectively are on sale about 25-50% below their NAVs at lowest valuation since 2008, as opposed to SP500 at all time highs.

I find that the Freddie interest rate is 90% correlated to the prior quarter 10-year Treasury, also shown in the graph.https://mf.freddiemac.com/aimihttps://www.treasury.gov/resource-center/data-chart-center/i...

Different investments help accomplish such like US Treasuries, and Life Insurance Policies. 

Stocks have so far fallen +1% and long dated treasuries are down +1.5%.The market may be starting to realize something else than just inflation.

And given that risk-free Treasuries pay 5.3% now, is a 5% premium over that worth it?