But there lies the problem. He's hammered "into them"and trained his defense to be exclusively zone. So if by some emergency he faces a KC, Baltimore or Rams team that starts exploiting that scheme, he doesn't have a backup plan because his players can't play man or his DL rarely stunts with pre- snap movement. You gotta have a D that has more than 1 pitch to get guys out.
I'd also argue that alot of these qbs you've listed (Tua, Purdy, Carr, Dak) are hardly elite and maybe not even "above average". Just because an organization is dumb enough to pay them elite money doesn't mean they are.