Some of that is not true.

At least with regard to the playing two FCS teams per year part. During Ferentz's tenure, Iowa has played one FCS opponent per year from 2005 to the present, with the exception of 2017 and 2019 due to the Big 10's rule about scheduling FCS teams. Iowa has played the following FCS opponents:

- Northern Iowa (2005, 2009, 2012, 2014, 2018, 2020)
- Montana (2006)
- Maine (2008)
- Eastern Illinois (2010)
- Tennessee Tech (2011)
- Missouri State (2013)
- Illinois State (2015)
- North Dakota State (2016, a loss)

You are correct that if you removed his 12-1 record vs. FCS opponents, he'd have about a .600 win percentage (.593 to be exact). His nonconference win percentage would go from .691 to .654. To be fair to Ferentz, he had a miserable first two years at Iowa. Since then, he's posted a .650 win percentage (.635 FCS adjusted).

There are rules about counting FCS games for bowl eligibility purposes which passed in 2012, but those games still counted in a coach's overall record prior to that.