BYU hasn't been taking their starters off the field at the end of games for the most part (a few exceptions)...they've just shifted away from exposive passing plays which are inherently more risky and more towards running plays and short passes which are lower risk.
Their top priority is to secure the win. RUTS implies continuing to call higher risk plays...those could potentially backfire and do the opposite of RUTS.
My point is that there's pros and cons and that Kalani's philosophy isn't just to roll over and send out the backups...they just get more conservative when they have the game in hand in the 4th quarter