The article said Iowa has a 91% chance of making the playoffs if they win out. That's a far cry from "an undefeated Big 10 team will never ever get left out of the playoffs".
It seems to me that the odds of Alabama, ND, Clemson, and one Big 12 school all winning out has got to take up a good portion of the other 9%. That means the likelihood of Iowa making the playoffs if those 4 teams all win out are close to 0%.