A few thoughts
1) The playoff team stats are also factoring in their playoff game or games. That means that some of them likely took a hit or two that the 2021 teams haven't taken yet.
2) UGA and OSU rank so high now that no matter what hit they take, they're gonna be in the same area as the national champs from 2017 to 2020 (rise of the explosive offenses)
3) 2021 Bama is at 2.07. That number was good before 2017, but it's lacking since.
4) 2018 UGA finished with a 2.11 net yards pp number. That's better than 2021 Bama even with a tough SECCG and Texas bowl game thrown in. It just makes me realize how lucky Bama is. OU was really good that year and Notre Dame was undefeated. That blocked us. OU does not look as good this year and Notre Dame has the one loss without many impressive wins. If we had that going on back then, maybe we get in. I hope I'm wrong, but there will be strong consideration for a two loss Bama if they keep the SECCG from being a blowout.
5)Look at all the teams ranked lower than 2021 OU and 2021 Okie State. Every one of them didn't just lose their semifinal, but were completely overwhelmed.
6) I knew Alabama was the best team going into last year's playoff, but by net yardage per play they were easily the best. All of the teams from last year's playoff not named Bama are on the bottom half of this chart.