This always made the most sense to me. Rutgers has played three while many Big Ten teams have only played two (and Michigan State has played zero).
Rutgers, Illinois, Indiana, Maryland, Nebraska, and Wisconsin have all played 3.
Iowa, Michigan, Minnesota, Nebraska, Northwestern, Ohio State, and Purdue have all played 2.
Those seven plus Michigan State was the logical arrangement for this year.
Now we need to get another P5 school on our schedule but time is really running out for that.