Specific detail of that sort is often accurate; though all references on the web, so far as I can see, were copied from the copy of Andy M Stewart's comment quoted earlier in this thread (apart from the sleevenotes on a cd made by an American player of the Celtic harp, which were probably copied directly from Stewart's songbook); so there is no corroborating information available. As I've said, I haven't seen vol III of Songs of the North (the first two are easy to find, but the third is not) so I can't say what details, if any, were provided.

Most of the tunes in Songs of the North were from traditional or older print sources; only a very few, I think, were modern compositions. The term "collected" is probably an anachronistic modern gloss of Stewart's, though; I doubt if Boulton or MacLeod would have used it.