Besides being a private insurance company, TIAA has the advantage of being a long-term investor.  That is, they don't need to sell assets that have (perhaps temporarily) been depressed below their likely long-term value.  That's one of the reasons for the hated restrictions on TIAA Traditional withdrawals in an RA account, with higher interest rates.  .e. You can't get all you money now, so they don't have to worry about marketability.

I'm not an expert on the insurance industry, but I sort of remember that the rules on marking insurance company assets to market are irritatingly (to us, as consumers) lax.  So TIAA may not "care" that some CMBS are impossible to value for a few months to a year.  Investment Banks that want to use their CMBS as collateral for loans or other purposes do care.  And no one wants to sell something that would provide a value that would (by pricing the security) mark down the rest of their holdings in that security!

Certainly, if any insurance company "lost money" on its capital assets, they would reduce what payouts they could control.  They can't control death benefits on life insurance, but they can adjust dividends and certainly the interest rate on TIAA Traditional.

But I really think there is no cause for alarm over the safety of our TIAA Traditional assets.

Tim