Could be a couple of things; (1)refs are trying to slow down Tennessee's offense so they can't score as many points as they have in Heupel's first two seasons, or, (2) They are betting on the game, taking the under, so they let the other team get away with penalties, plus call Tennessee tight to affect the score. I have noticed that as Tennessee gets closer to the end zone, the flags start flying.
One thing that would be interesting to know, in games prior to playing Tennessee, how many penalties have our opponents had called on them. There is where I think the evidence may revealed.