True, but their competition has benefited them.4 shutouts through 6 games is pretty hard to do.
South Florida - decent
Central Michigan - trash
Michigan - mediocre offense, scored 14 on them
Northwestern - mediocre offense, scored 15 on them
Kent State - trash
Michigan State - garbage offense. Ohio State held them to 10.
So yes, 4 shutouts in 6 games is impressive no matter what, but I also think it is a bit inflated in their case. They have not been playing athletic spread-style offenses.