That really only works when you play everyone right? Tough to do with 12+ teams.
Review 2003 through 2010 when the Big 12 had two divisions.
In championship games....
In 2003 it was 6-2 KSU instead of 7-1 Texas
In 2004 it was 4-4 CU instead of 7-1 Texas
In 2005 it was 5-3 CU instead of 6-2 Texas
In 2006 it was 6-3 NE instead of 6-2 Texas
In 2007 it was 6-2 OU instead of 7-1 MU
In 2008 it was 5-3 MU instead of 7-1 TX
Finally, in 2009 it was the two teams with the best records that squared of in the championship game...
From 2003 through 2008 the team in the championship game with the lower winning percentage cumulative record was 32-17 when it could have been 40-8.
Additionally, more often the championship game would have featured two nationally ranked teams. As it was the Big 12 Championship game in those years featured nationally ranked teams 4 of the 7 years. If you go with the two teams with the best record it would have been 7 for 7.