I don't think those teams are really top 10 teams, but they are very good teams. Northwestern obliterated Maryland, which Sagarin has as better than everyone BYU has played except Boise (and they're not far behind Boise). Its other 2 wins are against teams just barely below Boise and Michigan State is also barely behind Boise.
I think BYU should be higher, but claiming that other teams that have played an infinitely harder schedule than BYU isn't the way to make that argument.