You're right about the class issue, Shimrod; there'a also an age thing, isn't there? "Source" singers are old, and revival singers are -well, were - younger, or at least not quite so old. I know a couple of elderly singers who are/were revered and spoken of as if they were "source" singers, but who in fact learned their songs in exactly the same variety of ways as most of us do nowadays. Again, this is an oversimplification, but it's a general trend in the categorisation of singers.
Maybe we "revival" singers who were young in the 1970s will metamorphose into the "new source singers" when we reach about 75? We'll be respected, and regarded with interest, because we learned most of our songs from live performers, from books or from vinyl recordings, whereas the "new revival" generation carry theirs around on MP3-pods or whatever those little doofers are called. Our failure to keep up to speed with things like sound sampling and podcasts will be regarded as a charming, traditional quirk, a sign that we're part of a dying generation, and they'll be rushing to record our quavering tones before we die.

Marje