Yes, there is widespread uncertainty here in the UK about how to confirm a diagnosis of ME/CFS amongst many health professionals, especially those who have no specialist interest or knowledge about the diagnosis of ME, CFS, ME/CFS or SEID.
This is because there is no agreement or rigid guidance from any part of the medical establishment here in the UK (i.e. Royal Colleges, DoH), or CPD learning modules on the subject, as to which of the numerous options should be used. Even NICE makes no firm recommendation.
Consequently, many doctors (including CS) take a very pragmatic approach involving clinical judgement combined with information from criteria (Canadian, Fukuda, IoM, ICC, Ramsay etc) and guidance (e.g. MEA purple book, CMO WG Report, NICE guideline) that they are aware of, or have to hand on the computer or bookshelf
Incidentally, the number of doctors with no specialist knowledge or interest in ME/CFS who know about the Canadian criteria, or have a copy of this criteria, is very small indeed - so it hardly hits the radar