The 1954 definition eh? Well, it may have escaped a few people's notice but in the intervening half-century or so musical styles, definitions have moved on and evolved a bit.
Folk music evolves, story's change, like Chinese whispers, in the telling. When did the definitive version of any song you care to mention get written or first sung? Is the version collected in 1954 the definitive? I doubt it as it probably evolved over many years prior; how many versions of Arthur McBride have you heard and which one is definitive? The answer is none of them; they are all variations on a theme.
I really dislike narrow, exclusive definitions written by some dusty academic type and I absolutely disagree that, somehow, they are essential to understanding what defines the genre. Folk music is not about intellectual discourse but about performance. Categorization invites a narrow-minded attitude to music, encourages divisiveness and musical elitism.