That's sort of my point. If you can't say for sure who has, who can you say for sure who hasn't. I do believe that in most cases the cream rises to the top if they truly have the tools to be great, but it's hard to separate the coach from the QB.
Rodgers, for example. It's widely reported that McCarthy revamped his mechanics. Did he do it personally, or have his QB coach do it? Is that something no one else could do?
Those are all questions no one can answer. To argue that BB didn't develop Brady is a little extreme. Especially when Brady was no where near as good out of the box as some other guys. He steadily got better. Remember his game-manager days? Do you think he was capable of setting TD records then? I don't.