The state of Single Player games is so specific to stopping the game simulation that in both The Exiled Lands and my Isle of Siptah saved games, the door was still open from me last entering my dwelling before last Exiting back to Menu.

There should be NO way that the Single Player experience calculates Thrall Decay against the last date signed in, even if that option is set or if Building Decay is active. Dates for such things should always be based upon in-game time, not real world time.