I guess that depends - he may have a playbook of terrific plays he has developed over the years and understands WHAT he wants the offense to be, but can't teach it, or call the plays during a game that works during the flow of that particular game.
Hence good offensive mind - bad teacher, coordinator. He still seems to garner a ton of respect around the league, with his employer, etc. in short he talks a brilliant offense, he delivers a crap one.
As a GM/talent evaluator, he also says the right things - we need to get bigger, stronger, taller, as a team - but let's hope he doesn't fall into the Al Davis mold e.g. draft speed and to hell if they can play football.