When I read the articles that say transition in childhood helps gender dysphoria and is worth the risk, there seem to be two main points:
1) Adults who transitioned in adulthood tend to say they wish for themselves they had transitioned as children, in order to pass better
2) Young people who are part of community surveys and clinic data tend not to detransition
Since hormones, especially testosterone, cause major physical change, detransition is more complicated than if someone who had never taken hormones in the first place just changed their mind. So the low numbers of people expressing regret can also reflect the difficulty and burden of changing back, plus how the changes caused by the hormones would make one desire not to change back.
If the health risks are very high - which won’t be known for years yet for FTM since historically the procedure was rare - it’s likely that they will be reflected as high in middle age or older age - 50s and 60s. Some of the more recent studies have followed people for 10 years; but they are still following young adults. Most people don’t have heart attacks in their 20s and 30s. The trend of large numbers of girls taking testosterone from the age of 13 to age 80 and beyond is an unknown.
The adults who are unhappy in adulthood and wish they had transitioned as kids are impacted by their own life experience. There are hate crimes against people who are visibly transgender, and those who transitioned in adulthood are less likely to pass.
But the adults could also be projecting their own life experiences on people who are different individuals and would not have had the same life experiences, especially in a world that was open to diversity, where one would not have to rely on “passing” to prevent bullying and harassment.
If there were less stereotypes, there might be less dysphoria. Especially if the dysphoria is more about gender roles than it is about body parts, or if the dysphoria about body parts has its origin in early childhood emotional abuse related to not fitting gender stereotypes.
That abuse like that happens is clear; one of the gender hate crimes was against a little 3 year old boy whose father killed him for “showing signs of being a sissy”.
The embrace of studies designed to show hormones are worth the risk for kids - because of bullying, because of suicide - create a risk that the same hormones could be used for a different purpose if a different political party came to power. If they re-legalize conversation therapy, they now have lots of medical studies showing that it’s worth it to help kids completely fit gender stereotypes, using hormones, for the sake of their own mental health. So the homophobic murderous dad, in that future world, could take his son to get testosterone injections.