I'm not sure you have the order right.

An IRA can never be put inside anything else. Assets are put inside an IRA, not vice versa.

TIAA-CREF lets you buy an annuity inside an IRA (rollover, traditional, or Roth). But since a) this annuity has no surrender fees, you can convert it to cash at any time and just do a plain rollover to some other IRA custodian. Since it's inside an IRA, there are no tax considerations about converting it to cash.

There's no such law as "once an annuity always an annuity." It's just that the annuity issuer usually has big surrender fees making it impractical to cash in, and outside of an IRA the government imposes excise taxes on annuities used before the appropriate age.

WARNING! An annuity in an IRA is usually an awful idea because both the annuity and the IRA provide tax deferral. Most insurance companies charge a hefty fee for their annuities because people like the tax deferral. TIAA-CREF is one of the rare exceptions that charges reasonable fees for its annuities -- so reasonable that it makes sense to put them in an IRA.