Actually, I've had the same thought. On top of those factors is the fact that offense gets a lot more work in the "offseason" in 7 on 7s, which didn't used to be true. I don't think we'll return to the point where the defense is ahead of the offense at the beginning of spring...Normally, in August intersquad scrimmages, the defense is ahead of the offense.
Maybe this year, with a lot of first-year starters in the defensive secondary, they really missed out on the spring practice and that hurt them in the first few games. Maybe they are now catching up.