No doubt the Casgevy NICE guidance was super fast.
That said, the company evidence submission was June 2023 (well before MHRA approval, despite what some "experts" say is possible) and the guidance was issued March 2024, only 9 months after the evidence submission and 5 months after approval.
I would also not that the submitter was a BP (Vertex), that helps a lot as they know what is needed to do it right.