>>40303797hrt breasts aren't "gyno" they're breasts.
XY women with CAIS have vaginas.
Almost every single difference of secondary sexual traits are modulated by sex hormones.
If a mtf starts hrt before puberty they'll develop like a cis woman does during puberty. It's just that previously done changes can't be reversed.
If you start hrt at 40, all your bone plates are already fused, and your growth hormones are gonna be gone, so you won't change as much.
We refer to CAIS women as "chromosomally male, phenotypically female." There's no reason to be reductive and lump all transwomen into "biological males" except for political reasons. It's less accurate than other language we already have, and trans women vary wildly from those who never went through a day of male puberty and those who started intersex, to the person who started hrt 1 day ago as an adult.
Anyways, the idea that "sex is fully immutable" is just wrong. Presence of gonads/ovaries is immutable. If that's all you mean by sex, than sure whatever. But let's be honest, most people motte and bailey sex to mean "everything that makes a man look and act like a man" when bashing trannies, then retreat back to "sex only refers to gonads" when called out.