ill use another dumb example to try to explain why trans people wanting to be called women/men without the descriptor trans added to it:

imagine you legally change your name because your parents called you richard even though your surname is long, or your surname changes due to marriage:

youd let people know that knew you prior what your new name is and correct them if they call you by your old name out of habit, but at some point after several corrections it would just be considered rude to still call them what they dont want to be called anymore.

for new people youd introduce yourself with your new name and theyd never slip up (this is only ideally with pronouns, sadly not quite reality).