I don't think there's anything to it

Robinson was a run defender in DET and he's a run defender here. As Morris points out he is used more in run situations and Hoecht more in passing situations. Last week vs. NYG they called almost 60 pass plays. SJD and Gaines have earned more reps. Plus I think Robinson was not in late in the game last week. He'll get his 20-22 snaps/game and that's all there really is to it.