In 2021 BYU played a schedule that included 7 P5 teams. BYU went 6-1 with their only lose coming at Baylor to a team that finished in the top 10.
On the flip side, you do have a point. In 2021, 5 of those P5 games came against the PAC so we definitely have to weigh that into everything.
Going into the Big 12 it definitely won't be nearly as easy as their 7 games against the PAC have been over the last 2 seasons.