I suspect a bit of sophistry going on at the CCG. Some cleverclogs has discovered that Fiasp is just Novorapid - which is of course, prescribable - combined with Vitamin B3, which isn’t, unless there is some very unlikely evidence of a deficiency, whether or not it’s the same price.
It’s the same reason you never get prescribed pain relievers containing caffeine, which you can buy in any supermarket as Anadin Extra and such like.
The only difference, which the CCG is ignoring, is that the B3 has a demonstrable clinical benefit.