This is the claim from the Guardian article about this:
Puberty blockers and hormone treatment had been given to young patients despite a lack of research into their impact
Frankly I find that hard to swallow, given that puberty blockers existed long before they were used to treat trans people. Puberty blockers were used to treat children with extremely early puberty, their effects are generally well known. Sure, there’s always the classic “more study is needed” line in academia, but this almost presents it as careless implementation of a new drug, rather than a known and approved drug given to more people.