After studying this play well over a couple hundred views it is obvious that prior to the snap Tua knew exactly who he was throwing to on this play. He was not even looking at the 1,2 or 3 RW. His only intention was to hold the safety on the hash and then let it rip to Smith. He was going for the TD before the ball left the center. If you watch the video from behind and slow it down as I have done hundreds of times you will notice his feet, weight and momentum are all preparing to throw deep to the left side before he ever turns his head. The crazy part about this is he did not even look at the WR. He was throwing to an area on the field where he knew his WR should be. So there is no adjustment for the length of the throw. He knows if the safety stays put he is throwing a rope 48 yards down the left side of the field to the goal line.
I have never seen a QB set his feet, transfer his weight and step into a throw before he ever even looks at the receiver he is going to throw to. Well, Tua does exactly this on the play. Had Smith fallen down at the 30 the ball would have still hit the goal line. It took brass to even attempt that kind of pass in this situation or at the least it was a HUGE risk made by a true freshman going for broke. Not to mention his understanding of the WRs speed and their timing to have the ball dead on target even without first spotting his receiver.
He showed earlier in the game he can read progressions and keep plays alive with his feet while keeping his eyes downfield. Well now we can add to that. Tua can hit a target or area without even focusing on the target prior to the throw.