I suppose this is a pre-Internet example of fake news; people will believe false information if they want or at least prefer it to be true. In this case some will readily assume that a song is traditional when it was actually written by the likes of Alan Bell, John Connolly, Ralph McTell, Ewan MacColl, etc in a style that might well seem to be traditional. I daresay some of them might feel flattered at such an assumption, but not sure I wouldn’t be annoyed in their shoes; I get a bit pigged off when people pinch my jokes for their own stage banter, but maybe I shouldn’t.