Every P5 champion is guaranteed a spot. If the champion is in the playoff, then the runner up is guaranteed a spot. Most of the time, they are going to be in the top 12.

The highest ranked G5 conference champion is guaranteed a spot. Most of the time, they've been top 12. But there have been a couple of times that they weren't.

So what you're saying about ranking is true as far as the at large berths may be concerned. But it isn't necessarily true related to the guaranteed spots.

If you're hoping for an at large berth - then you're also hoping that the auto bid teams are highly ranked so that some conference champ ranked #15 doesn't take a spot away.