I had a classmate in high school that was on blockers for a while because she had early puberty, those studies make me wonder how she's doing now...
Honestly? Probably fine. GNRH agonists have a purpose in medicine, and not just as "puberty blockers." They're used to block sex hormone release during treatment of hormone-sensitive cancers, to prevent spontaneous ovulation during IVF, and yes, to treat precocious puberty.
The difference here is that when used as part of a therapeutic regimen, their use is time-limited, and the risk/benefit ratio is favorable. For example, precocious puberty can happen in kids at any age, some as young as
preschool. Aside from the social implications (can you imagine a 5 year old dealing with a period?), the health ramifications are significant. Early puberty means you've got less time to grow before your growth plates fuse, which means while you're outrageously tall for your age as a young kid, you end up a VERY short adult. For girls, early puberty means they can get pregnant at very young ages, with all the horrors that conjures. And for both sexes, it makes kids so clearly different and an obvious target for abuse. I clearly remember this guy in my 8th grade class who had a full beard. Like, the sort that most grown men can only envy. I used to stare at him and think, WTF went wrong there? He was indeed very short as an adult as well. Anyway, when used for a short course by an adult, or a longer one by a kid that hasn't actually achieved full puberty yet, most of the effects are reversible. Particularly the reproductive effects. In fact, Lupron is being studied as a way to preserve fertility in young women undergoing cancer treatment for whom there isn't time to attempt egg freezing: quiescent ovaries are less damaged by chemotherapy than cycling ovaries. Lupron returns the ovaries to a quiescent state similar to pre-puberty in an effort to protect them from damage.
For troons, particularly TIMs, they're on these drugs until they get castrated to suppress their testosterone. And for kids who are "questioning," they too are often shuttled onto cross-sex hormones and so need to continue these drugs to suppress their endogenous hormones. There's no end point. There's no stopping these drugs during the critical period during their teens and early 20s when they're laying down bone mass, and once that window is over, it is OVER. The description of these drugs as "puberty blockers" is disingenuous - most of the time, even the kids who start on these are already in or have completed puberty. The sudden blockade of sex hormones sends the TIFs into menopause and the TIMs into andropause, which causes its own problems. And then you're flooding them with high dose cross-sex hormones? Everything about this scenario is absolute lunacy.
TL/DR version: GNRH agonists have their place in medicine. Treating genderfeels in confused youth is NOT one of them.