That is right. My theory is that CBS have to cover the minimum 2 games from the Cowboys (or any NFC team) no matter what. In this past season, one of their potential scheduled game (Titans) was taken away because that game was on ESPN. So in order for them to get another game out of the Cowboys, they can cover a NFC matchup to cover for that. It seems like this happens when a NFC vs AFC matchup happens on NBC or ESPN. Another example would be the Texans. They played their week 3 matchup on Fox at home but because the Cowboy game was on Sunday Night, they were able to have an AFC matchup on Fox when they played Miami.