" I have said we can recognise a FOLK song by its style "
No we can't - folk isn't a "style" it's a process identified with a social group
Your list is how one of the most prolific composer on it describes himself - "a contemporary song-maker who makes songs using folk styles"
If he rejected the description "folk song writer" who the hell is anybody here to contradict him

Can't speak for all of them but I'm pretty sure Eric Bole doesn't describe what he writes as 'fok songs' - not that it matters too much
There's a not so slight problem here
Legally folk songs are in the public domain
How many on your list would be prepared to forgo the ownership of the songs they write ?
I know they all copyrighted their songs and I never knew Ewan to complain of other people using his without permission - but how would the rest of them feel about it ?
After he died, Peggy gave me a tape he labelled 'Chamber of Horrors' - about a dozen versions of 'First Time Ever' recorded commercially without permission or payment
Peggy said he didn't mind
Jim