///I doubt he'd ever have done that if he'd been formally trained, and yet the effect works beautifully.///

I don't see why it would make a difference. If it sounds good, I use it. I don't care if it's a real chord or not. The only difference is that I know when it isn't a real chord. Saying a person who knows his theory can't think innovatively is like saying Lewis Carroll couldn't have invented new words if he had actually known how to read and write--which, of course, disproves itself.