We've come a long way since 1939. However,
I would say he was generalising, and would say, if that is the case, he is right on this one. Unfortunately I personally think he chose a bad example in Willie Leonard. Like some of the similar ballads that came out of Northern Ireland, even though their earliest examples are from broadsides, I actually think some of these, Molly Bawn, Streams of Lovely Nancy, Fanny Blair etc., were locally made and based on real events, but we'll probably never know.

What he should have put and probably what he meant is 'memory not invention is largely the function of the folk' but I don't expect for one moment you'll go with that.