It makes so much sense when you have a first down between the 40 and 25 and don't have a great kicker, you already have planned for four downs. On third down, you have two plays called. If you don't pick up the first, you immediately line up and go on fourth down before the other team can change personnel and get lined up. At worst, you give up a few yards because you didn't punt like Bronco has since done from the 29.
That final pass to Pitta won the game for BYU. It was a smart gamble. I haven't seen Bronco as willing to gamble since then. A big part of that is he hasn't had a QB like Hall or a tight end like Pitta.
Still, doesn't it make sense for a team like BYU that has struggled for a decade with the kicking game to have a script that you practice to perfection anytime you get a first down between the 40 and 25?