I think you possibly misread what I stated. The fact that both songs contain the word 'Comber' doesn't make them the same song even if they tell the same story. There might well be some sort of influence there but they certainly are not the same song in any stretch of the imagination.
I fully agree with the fact that Bruce presented us with a mine of excellent info, but with anything it's as well to do your own research once you've found a wonderful source like that.
The misleading bit is where he first states that 'Whistle' is a 'version' of 'Next Market' but to be fair he then changes this quickly to 'variant version of the tale' which it certainly is. Trouble is some will jump on the first statement and start grouping the 2 quite different songs together. Such things even occur very occasionally in the Roud Index.