Phoenix, I belive the difference is that fact that you are doing a game with no victory conditions. In a multiplayer simultaneous game with no victory conditions if you exterminate all of the other players I believe you CAN continue the game by yourself with no problems. Everything will work fine. Of course it will be a little lonely.
But in a game with victory conditions, once they are met it appears some of the game functions simply cease to operate. The reason for this I believe is the game allows you "one more turn" so you can see all the scores and stuff and see who won. You can play beyond that point, but it doesn't allow you to do much. In a LMS game you know who won so the game code doesn't have to change anything.
Geoschmo