In light of the Yale findings, the most striking thing about the Cass review is that Hilary Cass was in no way qualified to conduct a systematic review, let alone lead a series of them. Look at her publication record! It takes experience and training to carry out an SR, and she has neither.
In the medical context, SR is considered to provide the strongest evidence (this can vary a bit in context, but is broadly true). As a result, SR findings are very closely scrutinised by highly-trained people whose entire job it is to evaluate evidence. And those are just "normal" SRs.
