Stewart wasn't having a great game. Pushing the agenda with 2minutes seems like a great way to have Memphis ahead at the half.
I strongly suspect BYU fans would have screamed bloody murder if Stewart had thrown a pic 6 or if BYU had gone 3 and out and allowed their great FG kicker a long try at the end of the half.
It wouldn't have bugged me if BYU had been aggressive, but the decision to sit on the ball seemed very reasonable to me.