you are probably right for those 12-team leagues that play 9-game conference schedules.
But I was right for the 12 team leagues that play 8-game conference schedules.
Its even less though for the SEC - they have a 14 team league but only have 8 conference games. That means besides their permanent cross-over opponent, they only play the other 6 teams in the other division once every six years, with a home game guaranteed against each of those other 6 teams once every 12 years.