Sorry Malcolm, it's you who have it wrong.
Iain's just got it different, - this is an evolving oral tradition we are dealing with, not an exam question.
Todays collations are the traditions of tomorrow. Just because at some point a "collation" was collected by Child, Greig, Bronson or whoever does not make that the correct "version", and render all that comes after it wrong. What a dreary stale old world it would be if we were only allowed to sing the "correct" song, and were not allowed any intellectual or emotional involvement in the recreation of each performance.
love, john