If a team is scoring on every possession, for example, their total yards for the game may be lower, but their offense will be incredibly efficient and put up a lot of points.
A couple of stats that are more telling are team passing efficiency defense and turnovers gained. In those categories, BYU ranked 105th and 81st. We were also bad at 3rd down conversion defense (83rd), sacks (115th), and first downs allowed (79th).
The defense may have been better than the offense last year (not hard to do), but they weren't good by any measurable metric.