Sinister Supporter: I take it the "He" in your quote is Bert Lloyd when you say "He does point out in the introduction that such alterations were being made, and in the notes it is indication how & where". That statement is incorrect. It should be forcibly pointed out, so there is no mistake: Bert Lloyd frequently rewrote traditional folksongs, and frequently did not point out that he had done so. Whether you approve of that is up to you. Personally I think anybody has a perfect right to rewrite folksongs, that is what I mean by the term. But I think Bert was betraying schoilastic principles when he didn't own up.
If I record a traditional song or tune, as I frequently do, I feel totally free to modify it in any way I choose. But if I write an article on "Traditional fiddle tunes in Cumbria, 18540-1860" (as I do), then I would feel it was an unforgivable sin to insert one of my own tunes into the article and pass it off as trad. There is a ditinction, I think. Bert Lloyd occasionally(and very felicitously) stepped over the line.