> with a tiny number of exceptions we have no idea of what our traditional singers knew or thought about their songs simply because hardly anybody bothered to ask them.

Okay generally true, but I'm going to question 'tiny' and 'bothered'.
Quite a few collectors, starting with what is generally considered the first revival, did go to some lengths to talk to particular singers about their sources. Those who didn't were too busy recording the songs, unfunded in most cases, and boy aren't we glad they did this. I'm sure had the collectors had the time they would have loved to have done this, so I think 'bothered' is the wrong word here.

Then there's the issue of the verity of the singers' statements about their sources, and here I would say it would be prudent to take each case separately and look at the possibilities and probabilities. As a collector I know how much the singers want to please and how defective memories can be. As I said earlier the overwhelming evidence is that the majority of singers learnt these songs in their youth and were being recorded in their final few years. Singers with only a few songs would easily recall where they got them but I would be more doubtful of those singers with large repertoires who had learnt them from several sources, print included, but maybe that's just me!