They still had a comparable RPI, better SOS, and better quality wins.
What about Washington in 2012? Finished with 24 wins overall, won the Pac-12 at 14-4, had an RPI of 54 (comparable) and a SOS of 63, and yet, they lost in the 2nd round of their conference tournament and go left clean out of the Dance. Now, Nebraska has a better win this year (on paper), but the precedent is there to leave a team with Nebraska's resume out.