Sharp is not talking about the words. Granted, he noted them down, but the focus of the piece is what sort of music should be taught in state schools

It is quite conceivable that the songs Sharp was looking for might have used words that largely derived from knowable print sources, set to tunes which had evolved in oral tradition into an idiom largely independent of the one they started out in. And Sharp would have been more interested in the kinds of melody his "peasants" had created or preserved. Did he make that distinction himself?