Respectfully, I think you're being disingenuous with regards to the facts and impacts of those facts. Pyne through 6 full games as starter has 100 yards rushing and ZERO rushing TD's. He's averaging 17 yards/game and has no points to show for it. While Book, over his last 25 games, averaged 41yds/game and scored 13 times. Book was good for a few more first downs/game with his legs and a score, every other game. That's significantly better. In 2020, Book ran for over 50 yards, 5 times. Through 6 games, Pyne has never eclipsed 50 yards rushing. Pyne's high output is 30. Book's in 2020 was 85. None of these are remotely the same.
If so far this season Pyne had doubled his rushing output while scoring 3 rushing TD's, and had 50+ yards rushing in 1/3 of the games, Notre Dame football is likely in a much better spot.