I'd suggest what traditionalists really mean is the definition plus the 'sound', the sound being a mix of instrumentation, delivery and subject matter but largely of context. If the 54 definition alone were the measure of folkness it would allow other music in because it was clear it met the criterion, as it is 54 is not used as a pathway but a keep out sign.

That's unfortunate because it means people go round the definition which lets in all kinds of wet, folk-lite, drippy acoustic music rather than genuine recent versions of folk, which may sound nothing like what traddies or the man in the street recognise as folk. It's not the definition that needs to change, it's traditionalist's expectation. It isn't The Definition or anything goes, people need to keep to the letter of 1954 then it'll be clear what is or isn't folk music. What they choose to call folk club music is of course up to consenting adults.