You are wrong. Not many P5 teams have a shot at the title under the current formant. The most important item on your playoff resume is your school name. ISU could go 13-0 and get left out for an 10-2 Bama or OSU team.
A 13-0 P5 team, even Iowa State, would not be left out unless there were at least four other 13-0 teams to choose from.
Now, would a 12-1 Iowa State team be left out for an 11-2 Ohio State... that's a different story. But no undefeated P5 time is going to be left out of a 4 team playoff.