Except that they are on complete opposite ends of the airplane and not able to speak to each other except over the interphone, which would disturb the Pilots greatly as they would be privy to the entire conversation.

Honestly, I think the Pilots and Flight Attendants are operating under an abundance of caution. Within the last month, possibly two, a Horizon FA had her back broken as she was slammed to the ceiling and then the floor during turbulence. This time of year presents a lot of opportunity for turbulence. Many times the Pilots have heard of turbulence from planes ahead of them and then it doesn't end up materializing for them. Do they risk it and let the FA's be caught standing in turbulence or do they decide to err on the side of safety and ask them to remain seated? I can see what the answer from many here would be but the Pilots have seen what bad turbulence can do and I think their decision is the best one.