West = 7 teams
East = 7 teams
Play all 6 division opponents
Play 1 permanent opposite division opponent (Alabama plays Tenn every year... South Carolina plays aTm every year)
Play 1 rotating opposite division opponent (so each of the other division teams once every 6 years)
So an east and a west division team only play each other once every 6 years unless they are permanent yearly opponents.
Since aTm and Missouri joined in 2012, my guess is that the schedules got bumped a bit and/or reset. Since South Carolina played Bama in 2010, they would have played again in 2016, but the addition of aTm and Missouri reset the rotating opponents.