Ye i dont know why people should legally be anything other than their biological sex either. Its also relevant for medical treatments
dont really see why it matters if some rando wants to have female on their driver's license or whatever
I think such matters should be disclosed privately ie have your doctor know about you being trans and not anyone else outside of like a bf ig
besides if they dont want medical treatment tailored to their sex why force them
plus human anatomy is similar enough across sexes that you can be treated for most things without problem, same reason why a veterinary can treat humans if an emergency requires despite only having knowledge of like dogs and cats