I was surprised at how low the Sagarin rating had BYU and thought it was absurdly low, so I looked closer at the data. The bottom line is that we don't really know yet how good BYU is. The schedule is looking much weaker than it did at the start of the season also. It is possible no team BYU beats will be in the top 25 this year. ASU is the currently the highest ranked team on BYU's schedule.
Here is how I would summarize what we know. BYU beat one good team and one bad team. They won with a good running game, no turnovers and holding the other teams to the high teens in points. They have not been explosive in the passing game, but they haven't needed to either.
They are a 3.5 pt underdog to ASU at home (after opening as a 2 pt. underdog). If they lose to ASU, they are likely not a top 25 team, although they could certainly still be ranked there with decent success going forward. If they win against ASU, they likely are a top-25 team and have an excellent chance against the remaining teams.
I think the main open question is if the passing game will evolve and more plays by more playmakers. Without Allgeier and Hall's running game, BYU would have a very different look.