I was hoping for a little more detailed discussion rather than conclusory assertion.
On the one hand, we have articles like
this one, which claims "Puberty blockers, GnRh agonists like the injectable Lupron or the implant Supprelin, suppress puberty by modifying hormone release. Such drugs have been used off-label safely for more than 30 years to stop early puberty."
On the other hand, we have articles like
this one.
Puberty blockers are used very differently for precocious puberty compared to their use with gender dysphoria.
Children prescribed blockers for precocious puberty are prescribed them when the onset of puberty falls below the normal range, and are on them for a relatively short time, then resume puberty within the normal time frame.
Puberty blockers for GD are prescribed to prevent puberty within the normal time frame and can be prescribed as early as Tanner Stage 2 of puberty, which can be 10-12 years. Even in not prescribed until age 12, most children stay on them until the begin CSH treatment at 16, which is much longer than when use for PP.
If the child then goes off blockers, they will be undergoing puberty outside the normal time frame and not in synchrony with their peers. The long-term social, cognitive, neurological and physical effects of this are not known.
Almost all children prescribed blockers go on to CSH, yet before the advent of the affirmation-only approach the majority of cases of GD resolved at puberty. Puberty blockers may prevent the natural resolution of GD at puberty.
If children go straight to CSH treatment they will never go through natural puberty. There is no evidence that treatment with CSHs produces the same effects as natural puberty, - particularly the effects on brain development, which occurs in complex stages during natural puberty.
The claim that blockers are reversible is false, even if children do resume normal puberty. The effects of not going through puberty during the normal time scale are not reversible, and the long-term effects of delaying are not known, since it is argued that puberty is a critical period for brain development.