Many of the FCS games have now been intermingled throughout the conference season as a way to provide another 'bye' week during the season. If the season is played, they need ways to push back the start of the season. And it's not like they can just reschedule all the games to try to move the vacated FCS games at the beginning. You're talking about over a hundred schedules to coordinate. Even the professional leagues don't have to deal with a crazy nightmare like that.