With UserPatch spectating, a rec game is used, but DE could approach this differently (I don't know how they implemented it, so they may or may not have done this). DE's server-based multiplayer would allow serializing the current game state on the server-side when someone joins to spectate. That way, the amount of data that needs to be sent does not change that much as the game progresses. It would also allow late join to be instantly live, while UserPatch had to play the game back at high speed to catch up.After a while you could, but there was a limit on how late you could still join. Iirc it had to do with the current size of the recorded game (spectating on Voobly is basically live watching a recorded game), I seem to remember the limit was 2mb.