how would you know it if you had not realized your partner was trans on other occasions (unless she later revealed it to you); couldn't this have happened to you too?
Of course, you have a point here... I can't be sure... But as much as HRT is a wonderful progress in many aspects of medicine ( and also a bit worrying given its potential side effects), I believe I can recognise on touch breasts grown out of HRT ... Not based on wide experience, but not insignificant.
Anyway, to each its own, as the saying goes, and respect for all!
Best
Dreams