Michigan had a hall of fame head coach that topped the F+ charts at Stanford (of all places) back in 2010 i believe
Freeman is producing better than any head coach at ND since Lou Holtz, but i doubt he's one of the greatest head coaches of all time in the business. Point being is that Harbaugh is an outlier head coach who produced an unprecedented run at Michigan. You can't count on on duplicating what Harbaugh did at Michigan because only one Jim Harbaugh exist. If your plan is to wait for a HoF head coach who bucks all odds and produces way above what the data says he should be producing, you are going to be waiting a REALLY long time.
Also important to mention is that after that really bad covid season at Michigan, Harbaugh's program catapulted into an elite team producing F+ numbers neck and neck with the best programs in the country for multiple seasons until ultimately winning a national title in 2023.