I think some of this “Belichick playing it close to the vest” stuff is a little overrated. I don’t think he’s holding back or really hiding much outside of maybe some gimmick plays, and even then, by this point, I think that tank is just about emptied out.
The easy explanation is that they wanted to use their power run game more than their spread passing game. We saw plenty of Wright against Detroit, the best run defense in the league. So I think his usage is more confined to the pass-heavy game plans.
That said, there are likely to be plenty of of pass-heavy games in the playoffs so I think we will see more of him then. And actually it will probably start this weekend against the Jets.