In theory, sure. But in reality, the committee will always find a way to exclude the G5 in favor of the P5 in the 4 team format.
As much as people don't like it, the committee DOES find a reason, and that reason is that the P5 teams have done a lot more. Beating one middling Big 10 team in the preseason, then maybe having one borderline ranked team in conference then a bunch of crap doesn't prove much.
The challenge in playing in the Big 12 is not that you play Oklahoma. It's that you play Oklahoma, Okie St., Texas, TCU, etc. No team brings their A game every week. The difference is for several weeks in the Big 12 if you don't play well you lose, even for a border-line playoff team.
A fringe playoff team can sleepwalk through all but a game or two with a typical G5 schedule. It's all the difference in the world, and why G5 resumes rarely impress.