Well, that the simple answer. UGA sat on the gaps , blitzed and pass rushed. They also shifted their front left to right right to left. They did this because they know the play is coming in from the sideline and JG cant change it. So what does this have to do with the QB ? He has to hit all the routes , but he doesn't consistently. So a defense sets on the run and brings more men than there are blockers. They play man coverage and dare the QB to fit it in a window. With JG they also count on him to hold the ball longer than 2.5 seconds.
If JG hit all the routes and delivered the ball consistently , then the linebackers would drop to coverage more and the pass rush would be pulled back . Its hard to measure the line when the defense has no respect for the short and intermediate routes.