Look at it this way: It isn't that he is turning to be turning; he is observing the action that needs to be observed, while holding a generally stationary position until he is clear of players. Since his focus is linemen, and they are generally all moving downfield, to maintain observation, he'll - naturally - have to turn his head, and, ultimately, his body, to maintain observation. The players will tell him when and where to turn and move. In some circumstances he may turn quickly; he may turn slowly; he might not even get turned at all. So, let the players direct your attention.
