The root cause of the difficulty is that 'folk' can refer both to style and to describe where and how that music came about. These meanings are incompatible, but they are both correct uses of the word. That is how language works, like it or not.

In common usage I'm afraid the second interpretation has all but vanished. To the 'man in the street', but also to non-specialist music journalists, broadcasters and retailers 'folk' describes a particular style of music which helps people to mentally pigeon-hole it more easily, and to look in the appropriate section of the record store. Other terms are used the same way and with equal lack of precision - most orchestral music is not strictly speaking 'classical', but that is a convenient catch-all term which is generally understood.

You would expect that a specialist folk music forum would be more comfortable with the more specialist usage, but apparently not.