Hmmmm...
You are assuming that the local software does nothing and that *every* interaction with the game (i.e opening a building, selecting with sliders etc...) is a server call - I doubt that. I would think it more likely the only server call is made when you click the ok button, whereupon your local Flash sends the relevant info to the server.
I'm not a programmer so I'd happily stand corrected, but it seems the most efficient way to me.