The theory is that the client communicates with the server for saves based upon in-game time not wall-clock time. So cheetah speed forces the client to talk to the server more often for this purpose.
I made my statement based upon my experiences playing. For one, I played the game for 3 hours disconnected from the servers - I knew my progress wouldn't be saved but I just wanted to play. It seemed to work fine aside from region play and that my progress wasn't saved.
Another time I lost my internet connection for 15 minutes. I continued to play. When I got it back, it claimed it re-sync'd my game with the server. As a test I logged out and back in and it all looked the same.
Maybe there is some simulation on the server side. But it doesn't seem necessary based upon my experiences playing the game.