If it came down to that scenario, PSU wouldn't have to lose to Rutgers. It would be a 3-way tie between OSU, PSU, and UM. Individual tiebreakers are thrown out in that case, and the highest ranked teams in the CFP poll goes to Indy. Which...would probably be Penn State. So UM does probably need Rutgers to beat them, but not because the tiebreaker.
Same reason we would have gone to the Big Ten Title in 2016, had Iowa not beat UM. PSU, UM, and OSU all would have had 1 conference loss. Tiebreakers would have been thrown out, and the higher ranked Bucks would have been in Indy.