Not an informed one, Jay. But I think the situation is analogous to a fiction writer and his/her editor. Can an editor make the first draft of a novel better and more accessible? Absolutely. Can an editor, having worked hard on making a novel a critical and commercial success, indulge the feeling that in truth it was his/her efforts that 'made the book' and 'secured the writer's success"? Yes, and sometimes they might even be justified in feeling that way. Can a very good editor understand the nature of the craft and the qualities of good story-telling in a very deep way? Sure, some of them can -- but they really can't know it in the most important sense and 'from the inside out' unless they themselves have sat in from of a blank page with nothing but a few ideas/characters in their heads and started typing those first few tentative words. IMO, there is a big, big difference between revising someone else's work and creating that work from scratch, even if the work is flawed or imperfect. In other words, there are writers and there are editors, and they have each chosen those fields and have proven themselves in those roles, and as long as the writer keeps writing and the editor keeps editing their respective roles remain the same. MD is a set-up man, an an excellent one; but Jones is the golf course architect. (Yes, he has 'revised' other people's work quite often; but he has also created his own from scratch).
Peter