I mostly do debt deals, so I'm wondering whether owning mortgage REITs gives me lending exposure or if I'm confusing myself

Mortgage REITs are a genuinely different business from equity REITs, and the numbers you've seen almost certainly describe the equity side. The FTSE NAREIT All Equity REIT index, where that roughly 9 percent long-run annualized figure and the 4 to 6 percent yield range come from, holds equity REITs. Mortgage REITs sit in separate indexes.

An equity REIT owns buildings and collects rent. Its risks are occupancy, rent growth, supply and management quality. A mortgage REIT holds mortgages or mortgage-backed securities and earns the spread between what it pays to borrow and what its loans pay. Its risks are the shape of the yield curve, prepayment speeds, and credit quality on the underlying loans. Mortgage REITs also tend to carry considerably more borrowing relative to equity, which is why their dividend yields often look higher and why their share prices can move violently when rates shift. High yield there reflects a leveraged spread business rather than rent from buildings.

So yes, a mortgage REIT is the most accessible public route to real estate credit exposure, and it's a distinct set of risks from the ones the equity REIT valuation-convergence discussion is about. That discussion, depressed valuations against both broader equities and private real estate, tightening new supply granting pricing power, is an equity REIT argument. It doesn't transfer.

One thing to check before you buy either: mortgage REIT distributions have their own tax character, and REIT distributions generally are largely nonqualified rather than qualified. A tax professional can tell you how that lands in your particular accounts.