You must have missed the part about Success at different levels not translating.
Totally missed the point.
Gerg - NFL Success + No College Success as a HC = Shitty coach
Shafer - No college sucees as a HC + Success as a coordinator and Position coach = Shitty coach
By the logic above, nobody that has had success in either the NFL as a coach or in College as a HC = Shitty coach.
Using that Logic, Saban must be a shitty coach which pretty much = everybody is a shitty coach.
Failed logic.
My only comment is that there is a difference between being a coach [in the general sense of the word], a coordinator, a position coach, or a head coach.
I don't think it can be disputed that GRob was a lousy head coach, by every metric / evaluative criteria imaginable. That doesn't mean that he can't coach or that he isn't a good coordinator. But as with every profession, people tend to get promoted to their level of incompetence [i.e., the peter principle]. That's where Robinson found himself.
No different than literally hundreds of other coaches who are good at their jobs, but fail when they get promoted and are suddenly over their heads. A guy like Romeo Cronnel is a perfect example. Tremendous defensive coordinator. Well liked. Obviously, a great coach [in the general sense]--which is why he continues to get jobs even after a couple of failed stints as an NFL head coach.
Him flopping as a HC doesn't mean he's a "bad" coach, it just means that he isn't a HEAD coach, and a guy who's better suited for a DC role.
The logic you list above doesn't apply to Saban, because even though he was mediocre at the NFL level, he's had an incredible track record as a head coach at numerous other stops, before and since he made the jump the pros. The same can't be said about either Shafer or GRob. Sure, they had solid accomplishments AS DEFENSIVE COORDINATORS, but certainly not as head coaches. When they got those opportunities, they failed to deliver--hence, why they are viewed as poor head coaches.
Doesn't mean that they can't thrive as coordinators, or as position coaches, nor is it a reflection on their overall general coaching acumen. Being a head coach brings a lot of additional diversified responsibilities that are beyond many in the profession, who lack the chops for it.