There are a world of outcomes, but a limited number of ways to manage a game. Fox is going to win as many games as possible and this is how he believes he can do it. He's 2-1 with Mitch. One would expect the playbook to open up both as the kid improved and game situation dictates. For the moment, it's been demonstrably effective, and it's hard to argue with success.
Personally think winning is unimportant this season and developing Trubisky is paramount. I still have hopes that there are plenty of games this season, and by seasons end it will be a very different offense. Teams rarely, almost never have an opportunity to bring along a QB this deliberately.
IF it works, how can you argue with it? From a 'you ain't getting this kid good enough to take you to a Superbowl this season, so get over it' point of view, taking time makes sense to me and I don't care that he won't be ready to go into a shootout with New Orleans if the D comes back to earth.