I think there is an over-emphasis on the folk 'process'.

Songs were transmitted orally (thus rendering them open to adaptation) not because people thought that it was the 'done thing' or 'traditional', but because there was simply no other way for them to do it. The means of noting, recording, archiving, distribution etc were simply not available then.

BTW bubblyrat, Mr Sharp did indeed 'edit' some of his collected songs.