This only impacts people under 18, and only concerns actual medical procedures, surgery, drug treatments, etc for gender re-assignment.
People are still free to let their kids cross dress, have their kids go to therapy about changing genders, and everything else. And once they hit 18 all the restrictions drop off and the people in question can cut off the twig and berries, get boobs and take all the estrogen they want.
If a kid wanted to chop off his hand or foot, we wouldn't let them, the same applies here.