Great letter, thank you for sharing.
I particularly like that this is the lead point about the dangers of PBs:
So-called ‘puberty blockers’ target the pituitary gland and could have damaging effects on brain development. They interrupt natural developmental processes and interfere with normal adolescent brain changes crucial for social bonding, emotional regulation and learning to think independently.
The impact on fertility and bones is bad enough but brain development (or lack of) is fundamental to successfully growing up from being a child to being an adult.
Unfortunately, it does seem to contain misinformation about the use of PBs in precocious puberty. It's not typically a 6 month period, it's until an age when puberty would be more appropriate. So a 3 year old who started puberty might be on them until the age of 8 or 9.
The key point being that puberty is allowed to start and complete in this scenario. Whereas in their use for gender dysphoria, it is not. PBs are taken throughout the expected development window of the physical changes that would be expected during puberty. Stopping them after the age of 17/18 (by which point cross sex hormones might also be being used, to create a synthetically-induced copy of the secondary sex characteristics of the opposite sex) will mean that crucial brain development has been entirely missed - and can never happen. Here's Sallie Baxendale on this: