Barbara, Dar, thanks for the replies.
That does better explain how the timescale affects the game, although it does tend to say that the village is much more efficient offline.
I think I figured it out now: offline timescaling (probably) does not take into account the roundtrips that the villies make to move materials when you're in-game.
SO, the sooner you clear the field of crops, the sooner the harvest resets, and so on.
Try comparing the time it takes to clear the blockage. When you're active, it takes around 10 minutes to clear a few percent, whereas offline the whole thing is done in about an hour.
-Matt