They lost to Utah St. on the road in 2012. Utah St. was pretty good that year finishing ranked #16 in the country. Utah is 2-15 in road games vs. teams that finished ranked since 1995. (BYU is 2-19). It is not even remotely surprising that Utah lost that game.
All of their other losses before and after BYU came against Pac-12 teams that finished with winning records. Over the last 20 years Utah is 9-25 .264 win pct. vs. Pac teams that finish with a winning record. Losing to quality teams in the Pac is what the yewts do. The fact that they won 3 games against such competition over the last year is nothing short of a miracle. (BYU is 5-11 .312 vs. winning Pac teams over the last 20 years)
If Utah was losing to teams that they SHOULD beat before and after BYU, then that point would have some validity. However, given the state of the Pac-12 there aren't many teams that Utah should beat.