Suspect persistence rate in people who were endorsed as "in the wrong body" since toddlerhood will be fairly high--especially if they "go all the way" w/full medical transition. Docs are increasing persistence via full affirmation in toddlers; it's all they will have ever known.
It's a combo of social transition & (later) blockers. Imagine being 3 yrs old, everyone around you saying, "yes, you were born in the wrong body, you are really a [boy or girl, as case may be]." Why would you desist, after years of that? Then blockers & exactly what you said...