I do not subscribe to this theory, and the main reason is that when teams get up, they tend to come out fast but can't maintain it for 4 quarters. So they use the intial burst to jump to a lead then hang on.
And in the BYU-Utah series, that simply does not happen. BYU tends to come out quicker and plays better early. BYU led the 2011 game until just before half, then got pwned in half 2. In the 2010 game, BYU came out quicker, led for 3 quarters, then lost it late. In 2009, BYU came out quicker, then tried to hold on, and barely did in OT. In 2008, Utah did start quicker, but BYU held on in half one, then half 2 happened. In 2007, BYU started ok, was tight most of the way, then Utah scored late, with BYU wining it later. 2006 was close and back and forth all gamem until BYU pulled it off late. 2005 is the exception.
Point to this is that in the Bronco era, other than 2005, Utah has really been the better second half team, with BYU being the better first half team. I think that draws that thought process into question. But what it does do it put coaching and half time adjustments into the spot light. Clearly Utah has been the better team in half two in 6 of the last 7 games in the series, so it is no wonder they won 4 of those 7 games.
BYU has to be better in half 2. That is the issue. BYU has to close better.