I'd be more inclined to believe that Garrett would have benched certain players a bit back and was "discouraged" from doing so.
Supposedly Bruce Carter's effort is in question. That's not something that just happens overnight and it's likely he's been slacking for a bit if all those rumblings are correct.
I was going to post the other day that players in Dallas don't get benched because they are bad. That, in and of itself, won't get you benched. Players get benched if they have piss poor attitudes. Marion Barber was "benched" because he didn't follow dress code. Kevin Ogletree made mistake after mistake and yet was given chance after chance, likely because he wasn't disgruntled IN ADDITION to be unproductive.
I would suspect that Bruce is in the doghouse and his benching has more to do with that than it does the team thinking he can't get the job done.
For Morris, I think he's done a little too much skirting responsibility. Having Stephen tell you to step up while you are saying it's a scheme thing isn't what Garrett would want to hear.
I don't think Garrett really sweats what might happen after week 17 right now. He'd likely be sinking himself by interrupting his process with changes just for the sake of his own interests. How are you going to preach accountability and responsibility and then make self-centered decisions that go against what you have been preaching? Doesn't work.