Not only is BYU 4.5 on over/under for wins, but most books have them at +110 for the over. What does that mean? It means you have to bet $100 to win $110. They are telling you that not only is the line 4.5, but BYU is more likely to win 4 games than they are 5 and they adjusted the lines accordingly.
As for Utah, they are -160 or so on the over, which means they think it is far more likely that Utah wins 10 or more games rather than 9 or less. You have to bet $160 just to win $100 in order to play the over.
So if you bet on BYU over and Utah under, you are getting really favorable odds. In other words, it’s the opposite of what you are saying is most likely. At least that’s how the experts feel.
I never bet on my own team. Too much stress. But I enjoy looking at odds that are created by the smartest guys in the business. They are far more accurate than what I or you or any other random person could predict. I use it as my starting point for whether my team exceeded or failed to meet expectations.