You can't have a good point differential averaging 20 points scored per game.
Even the best defenses ever allowed like 10 ppg. So with such a low scoring ceiling, the variance isn't there.
This year, looking around at other teams, Miami has a +8 ppg differential. They're 6-5.
A&M, with their fired HC, has a +15 ppg diff, with a 7-4 record.
Yeah, in the 2023 context, Iowa is a godawful 9-2 team.