Why did RAF keep using its own Pilot's Notes/manuals when better ones available?

[RCnoob]

Originally Posted by MW Giles

Suggested reasons for RAF doing its own manuals

5. The RAF manuals were written by AM not the manufacturer

Just some suggestions

Martin

What is AM? Indeed I have seen no indication that the manufacturers wrote the RAF manuals.
The Americans had an odd system. Each manufacturer wrote a manual for the aircraft, but the official USAAF manual was a completely different document. Initially the US Navy used the manufacturer's manual, but then they switched to the USAAF approach.
Roger