I really don’t think it’s a choice. However that doesn’t mean that it isn’t some sort of disorder. Depression isn’t a choice. Or OCD or Bipolar Disorder or any number of other afflictions, for that matter.
It is a “choice” when kids are being taught by instructors to “experiment” and “fantasize about who you’d like to be romantic with among ALL of your friends”.
Encouraging them to cross-dress and enter the opposite sex restrooms, etc.