Because medical processes are required to complete the transition.
Not in the least. There is no need to transition unless there is a dysphoria - meaning a dissatisfaction or anxiety produced by the feeling of being mismatched with one's birth sex. If one doesn't have the dysphoria, then by definition that means that one is comfortable feeling like a woman in a man's body. And, of course, your side is supposed to accept that. Your side says flat out that gender isn't sex, and that one's gender doesn't have to match one's physical sex, and sometimes it fluctuates back and forth -- gender fluid - where one feels man one day, and woman the next. You can't "transition" in that example, right? And, if the person is not dysphoric, then there is no treatment necessary.
A girl who feels like a boy (whatever that means to her) doesn't need to be surgically altered to physically appear like a boy. The person is fine the way she is. And, that's consistent with gender ideology which says that a person can adopt another gender without transitioning physically, and live that way. Gender identity, after all, is just the social construct of what it means to be a man or woman in a given society. In another society, the social construct might be completely different, says gender ideology.
BTW, there is a difference between a "disorder" and a "disease". As an example, a broken leg is a "disorder" and is one that, very frequently, has "doctors treating it" - BUT it is NOT a "disease".
Sure,, but a person who likes feet sexually, and is otherwise not bothered by it, does not have a disorder. The person is fine, with a predilection for feet. Whereas someone who likes feet that way, and suffers anxiety as a result, needs psychological treatment to help with that. Similarly, a person who says they are a man in a woman's body, but who has no anxiety, depression or adjustment issues about it, doesn't need treatment in any way. There is nothing to treat.
Quite frankly I have no real concern with either promoting or suppressing "gender realignment" for any individual provided that there is no element of compulsion involved.
An adult can do whatever elective plastic surgery they might like, as long as doctors are willing to do it. My only concern on that front is that the gender ideologues need to leave the kids alone.