This is of course a horrific move motivated solely by bigotry. There's zero evidence that puberty blockers are harmful, and the prescription of them to trans kids was supposed to be a compromise with cis society rather than allowing trans kids to go through the correct puberty alongside their peers. While they are technically being used off label in trans kids (when actually prescribed, there's less than 100 kids in the country taking them because the GIC system is effectively a denial of care), the posology isn't changed. But, that's what happens when service reviews get hijacked by ideologues who believe the service shouldn't exist (part of the cass advisory board is Riittakerttu Kaltiala, part of a body (SEGM) dedicated to trying to protect conversion therapy).
Worth noting as well that this is the next step in the road towards the far rights ultimate goal of bringing down bodily autonomy entirely. This cannot be considered separate from the overturn of Roe and the case going through the Texas 5th circuit at the moment to require parental consent for birth control in the US, and the increase in women being tried for abortion in the UK (as it's just decriminalised) and attempts to overturn gillick competence