Tangentially, it strikes me that the turn back to source singing is a very recent development. Back in the second (Fairport) and third (Steeleye/Horslips) generations of the revival, the early revivalists were seen as, if anything, too reverential towards their sources. Writing about Skewball, Maddy Prior effectively claimed Bert Lloyd as one of the good guys because he'd changed the source material:

Martin (Carthy) assures me that this version comes from the influential repertoire of Bert Lloyd. Bert had a wonderful lyrical sense of the traditional and was not hampered by false loyalty to any rigid idea of how it "should" be. He consequently greatly enriched the music for us all.

I guess it's a generational thing: we're far enough from Bert Lloyd's heyday to see the Revival as an event in the history of traditional music, rather than as a process that we're still contributing to. Hence the recent revival of interest in singers like the Copper family (how many years did the BBC have to make a documentary like "Coppersongs"?)