better for P5 conferences would've made the playoffs. In the last 4 non-Covid seasons there were exactly 0 teams with only 9 wins that made the playoffs. There were 3 teams that were 9-3 that made it in 2018, but there was lots of parity after the top 5 that year and only 1 single 10-2 P5 team failed to make it (Washington State who had exactly 0 wins against ranked teams that season).

Looking at P5/P4 teams that were 10-2 or 10-3, here's how it would have broken down:
2023:
Missouri (10-2) - IN
Penn St. (10-2) - IN
Ole Miss (10-2) - IN
Oklahoma (10-2) - OUT
Louisville (10-3) - OUT
Iowa (10-3) - OUT

2022:
Alabama (10-2) - IN
Tennessee (10-2) - IN
Penn St (10-2) - IN
Washington (10-2) - OUT

2021:
Ohio St (10-2) - IN
Ole Miss (10-2) - IN
Michigan St (10-2) - IN
BYU (10-2) - OUT
Oregon (10-3) - OUT
Iowa (10-3) - OUT
Oklahoma (10-2) - OUT
Wake Forest (10-3) - OUT

2019:
Wisconsin (10-3) - IN
Florida (10-2) - IN
Penn St (10-2) - IN
Alabama (10-2) - OUT
Notre Dame (10-2) - OUT
Minnesota (10-2) - OUT

2018:
Michigan (10-2) - IN
Florida (9-3) - IN
LSU (9-3) - IN
Penn St (9-3) - IN
Washington St (10-2) - OUT

So basically 50% of P5 teams with 10 wins would've ended up making the playoff. SEC and B1G teams with 10 wins are almost guaranteed to get in above 10-win teams from the B12 and ACC. In fact, 10-win teams from those conferences got in roughly 75% of the time whereas 10-win teams from other P5 conferences got in 0% of the time. If we went back 1 more year that number would increase to
about 15% so it is possible, but it is much less likely.

In short, if a B12 team wants to get into the playoff as an at-large then they need to likely win 11 games. However, if they are 11-2 to at the end of the season they are almost guaranteed to make the playoff. However, it is possible for a 10-2 team from the B12 to make the playoff if a year like we had in 2018 happens again with fewer 10-win teams than normal.