18-20 is fine if that’s the starting point where they go to the gp to get referred for counciling to start exploring their dysphoria for the 2+ years most therapy is recommended for prior to looking at ‘living’ as the opposite gender then starting the hormone etc transitioning after a solid time living as the prefered gender.
18-20 to get hormone blockers and other irreversible changes is madness.
Self id law makes the chance of safe slow transitioning zilch, if there will be any medical or mental health transitioning available at all, given that all it will take to change gender is signing a form then zero medical treatment necessary.