The requirements for training documents are stated in UK CAA Standards Document 55
This would be the "
Guidance Criteria for the Approval of Training Organisations Offering Courses of Training for Pilots Licences, Ratings and Certificates" (i.e. 'guidance' and not 'requirements') which, in any case, has no relevance whatever to Registered Facilities or 'Declared Training Organisations'
The same material is undoubtedly included in some EASA document
No, it isn't. This is just the UK CAA's opinion of 'best practice' and, whatever its merits, has absolutely no validity in law. It's what used to be referred to as 'gold plating'.