Printed collections of dance tunes (a great many were published over several centuries) were an important source for a lot of vernacular musicians as well; nothing new in that. Musical literacy was actually more common in the 18th and 19th centuries than it is now. See the Village Music Project for MS tunebooks kept by a lot of musicians of that period; these were a mix of tunes noted by ear and copied from print.

Sharp did note some dance tunes in Appalachia, but he was mostly there for the songs and didn't have a lot of time; so he concentrated on the latter. So far as the dance tunes he published are concerned, my memory is that he said which tunes were taken from print and which from tradition; all you have to do is look at the books, which are not hard to get.