They were #7 AP (pre CFP rankings) when LSU beat them handedly......
If LSU finishes 11-2, they will have wins over 3 Top 7 ranked teams...... No one else would have a resume that comes close to that.
Put it this way if you want to look at the season as a whole instead of when they played the game.
LSU at 11-2's 3 best wins would be UGA, Bama, Ole Miss. Their combined record in regular season likely to be 31-6 at best (includes 1 Conf Title game)
LSU at 11-2's 2 losses would be Tennessee and Florida State. Their combined record in regular season likely to be 19-5
Say USC wins out at 12-1.. Their 3 best wins would be UCLA, Oregon, Notre Dame. If that happens, their combined regular season 27-10 at best....
While USC had some solid wins and would stack up against most other teams in the country, LSU has the ace in the hole with theirs.
I think that is why the Committee is basically giving LSU a spot to win and in or lose and be eliminated.
Since committee picks the Cotton Bowl, I could see them slating LSU to that if they lose to UGA.