I think that your first paragraph should have been in quotes, Cap'n. I read it through and thought, 'I've read this somewhere before - the Cap'n's not guilty of plagiarism now, is he?' Then I read the attribution and all was well ... Well, relatively well!

I recognised the quote because it is from a wise and brave article by Mike Yates - but I suspect that you're misusing it because you desperately want to 'prove' a point. The terms 'traditional' and 'revival' as applied to singers are necessarily fuzzy. I'm sure that if you dig deep enough you can find a few more exceptions. But exceptions don't 'prove' anything - they are just that - exceptions!
On the other hand it is possible to point to many more examples of people who fit the categories exactly. I, and many of my friends and acquaintances, for example, are 'revival' singers; Harry Cox, Sam Larner, George Maynard et. al. were 'traditional' singers.

A couple of things from the article by Mr Yates which I urge you to re-read and to think about:

(i) "At the end of the day it doesn't really matter whether or not Bob Blake was a 'traditional singer'."

I'd agree with that - at least it probably doesn't matter in an aesthetic sense - but distinguishing between the two types of singer is still useful (if not essential)in an interpretative sense.

(ii) "Also, many people today want a world of certainties, a world where our every thought and desire can be seen in terms of black and white."

Forgive me, but that passage could have been written for YOU, Cap'n! You seem to want to abolish the useful categories, 'revival' and 'traditional' because of the existence of exceptions (well, in this case, one exception). Some of us are more ready to put up with the "unsatisfactory nature of things" rather than to recklessy discard useful categories.