The point isn’t that it was a QB throwing a pass. The point is that Luke wasn’t coming in to take over for Adrian and be the QB for the rest of that game or even that series. He was brought in to run that specific “gadget” play which was designed specifically for Luke. That’s why basically it was a trick play. If the pass had been incomplete or Iowa’s DBs stayed on Spielman and Luke ran the ball for a few yards, he was most likely returning to the bench on the next play. That’s why Adrian went back at QB the next offense play/drive after the Luke TD pass. If Frost were trying a different QB to test something out with the QB’s, Luke would have came back in at QB the next drive. But, because Adrian came back in, it shows that the play was basically a trick play and Luke was only used for that specific play.