I know that all this is word games. Do you know how I know?
Because I have lost count of the number of times I have seen trans activists refer to people they don't know, on sight alone, as AFAB or AMAB. If they really believed any of it, they would say they couldn't possibly know what was on any stranger's birth certificate, unless they'd attended the birth.
But as it is, they look at someone and say instantly, "AFAB". Really, how do you know, eh? Maybe she was "AMAB", surely? Except they know that doesn't happen!