Not to muddy the waters too much, but there are some examples out there of offensive playcalling HCs making the title game or CFP.
2006 and 2007 Ohio State (Tressel)
2010 Oregon (Chip Kelly)
2012 Notre Dame (Brian Kelly)
2013 Auburn (Malzahn)
2014 Oregon (Helfrich)
2014 FSU (Fisher)
2017, 2018 and 2019 Oklahoma (Riley)
2020 and 2022 Ohio State (Day)