I think it's easy to argue that OU shouldn't be in because their offense is objectively bad. Only one game where they scored 26+ against a P4 (Tennessee). 3 of their wins are against Temple, Kent State, and Illinois State. They were beaten soundly by Texas and were beaten by Ole Miss. They rely solely on beating Alabama by 2 where they had a post game win expectancy of 5% and had half the yardage of Alabama.
Thing is, they would still push another SEC team if Oklahoma or Alabama wasn't in it. The SEC is extremely broken (likely intentionally) because so long as they play a pathetic OOC schedule, only play 8 conference games, and rank a majority of the teams to start the season, you'll have almost 6+ "playoff contenders" at the end of any given season.
Like honestly the fact that the top teams in the SEC, Bama and Texas, lost their season openers to OOC opponents in much worse fashion than ND should be hurting the conference as a whole. Instead they pick up a couple more in conference losses and stay in the race, WTF.