I am not sure about using dictionary definitions as proof, though.
We do use a lot of words wrongly and also avoid using others to spare people’s feelings.
Spastic was a perfectly respectable word to mean a sudden jerky movement; we tend not to call people that these days. Moron used to refer to a person who failed to attain a particular IQ score but, again, most parents would not like it if a school report referred to their child as a moron (even if it were biologically 100% true).
Even doctors use the word ‘weight’ incorrectly and would probably be surprised if you have your weight (correctly) as several hundred Newtons towards middle Earth.
As for ‘sex change’ operations, people also refer to getting ‘bigger breasts’ when breasts cannot actually be enlarged by an operation, merely their outward appearance changed by the insertion of a man made sac.
Sex, clearly, has meaningful implications, though, so merely redefining it to spare someone’s feelings cannot be done lightly.
Where sex matters (sport, prisons, the science lab, medical settings), we should be careful to be chromosomally correct. If someone wants to refer to themselves as having ‘changed sex’ I would no more take offence than someone referring to their ‘new breasts’.