Aha, It has the hand of the maestro all over it! Very little in SOW wasn't touched up by himself. I don't think you need look any further.
Had a similar incident with Richie regarding Child 295. SBG sent Child a concoction of 2 separate ballads, one The Brown Girl off a garland and the other a version of 'Sally and her True Love Billy' he had collected.(295B). Richie collected a version of 295B the concoction word for word from a family in the States who were claiming the song had been in their family since the early 19th century! Hmmmmm! That Tardis gets a lot of work!