My first thought is to throw this in with the Madden curse and black cats. Superstitious crazies.
However, if you think about the primetime games, they typically want great football. Unless that is Pittsburgh/Baltimore, you are probably going to see good offensive play in most those games. Meaning if NONE of your players are even starting a 3pm game, either you have no west coast players or you just don't have players in games expected to score a ton of points.
I still think it's nonsense, but that's the only logical argument I could think of for this theory.