I may be wrong on this, and so look forward to some discussion, but I think it must be far easier to be an NFL OC than doing it in college. First, all you're dealing with are the best of the best, they know how to play and know that learning and doing their job is key to keeping it. Second, longevity. NFL doesn't have to start at ground zero and teach upwards - just their individual schemes. Makes it a lot easier seems to me. And third, then you let them play while you sit in the box with your hat on backwards doing whatever. They know what to do and if they don't, the position coaches on the field get their attention. Once you tailor a game plan to your players, all thats left is making adjustments for what the defense does. Again, player experience goes a long way in picking that up.
A college OC almost has to be "hands-on". He has to tailor his plan to the various levels of player skill sets that constantly change. It helps if he knows what those individual skill sets are, but I digress. BoB coaches just like he's in the pros: "I went over the game plan and now they need to execute it." He expects the players to understand situations and adjust on their own and I dont think college players can for the most part do that.
So it's easier to "fall up" for him. Its how he coaches anyhow.
Hope this makes sense.