GM's don't get involved with the gameplanning. They hire coaches that run the system they want run. What they might do is make suggestions for what they want, such as a particular player needs to be more or less involved or the offense needs to be more balanced. But they don't actually get into the specific gameplanning...quite frankly, no GM has the time (and for the most part expertise) to get particularly deep into the specifics of what the coach is or isn't doing. That's why they hire the guy that's going to do what they want without having to micro manage.
i know, that was my point.