I forget the exact percentage, but something like only 20% or 30% of teams make it through an entire season with their starting QB not missing at least some time due to injury. It’s not really unique to Utah.
Actually it was all the way back in 2016. In 15′ they sat Wilson against Fresno for precautionary reasons to get him ready for Oregon. Your point is valid but I have no earthy clue how to prepare the #1 the way he should be prepared while getting the #2 enough reps to have him ready to go.