Here's my understanding that I gleaned from other replies to my question, elsewhere in this forum, and some additional reading.
FIrst, the IRS gets information from the retirement account company both about regular retirement plans and annuities. They can tell from this whether you took the required RMD or not. Immediate annuities, like the ones I have, do not involve the usual RMD process because the annuity payments are treated as automatically satisfying the RMD requirements for that retirement account. Again, the IRS has all this information. I don't have to say which 1099-R goes with annuity/pension vs. 403(b) etc because the IRS already knows.
So in other words, all of the 1099-Rs I got involve payments that go towards RMD requirements. So the correct answer to "is this an RMD?" is indeed, "yes". And the next set of questions from TurboTax clarifies the situation further. Finally, since the requirement income here is all taxed at the same ordinary income rate, for purposes of computing the tax, it doesn't matter which was pension, annuity, or 403(b) etc RMD distribution.
I do think the TurboTax question could have been more clear. But I'm good for now.
Thanks for your help, everyone!
