There are only two possibilities here:
1. There's more than meets the eye with the Perry situation, whether it has to do with the vids or something else, and his eligibility may be in question behind the scenes which is the true reason he isn't playing. Weldon suspended and maybe they don't want to burn JW's shirt by playing him more than 4 games this season, leaving Rosier as the only option in their eyes. Richt is falling on his sword and taking all the criticism until things get hashed out, like a good CEO.
Plausible and not out of the realm of possibility but I'm not holding my breath.
2. CMR is senile. Also plausible.
If Kosi continues to ride pine and Weldon starts getting burn after his suspension is up, or JW after the Duke game (preserving his RS eligibility if he doesn't play in that one), that could be telling.