SO why force them to have body changing surgery before they are adults?
Well first you'd have to be right that "forced body changing surgery" is happening before adulthood.
1. you can't FORCE surgery on minors, parents have to agree to it.
2. Surgeries HAVE to be discussed, presenting both pros and cons to said surgery, and the patient makes the choice. If a teen under 18 (or even 16) tears their ACL and needs surgery to repair it, parents are consulted. If they need plastics due to an injury, parents are consulted. It is actually not allowed that doctors "force" a surgery on ANY patient without consent, of the patient or parents (or both depending on age). A doctor would lose their license if this happened.
3. It is best practice NOT to do any body modification surgery on anyone under 18 UNLESS medically needed. A NMR - not medically required - surgery won't happen on anyone under 18 UNLESS the situation warrants it, (reduction in breast/chest tissue for teen boys, for example, who get chest surgeries in higher percentages than trans boys do, but would for very similar reasons).
No one FORCES surgeries on minors. How many times do you need to be told this?