Most likely Ducey was not above his auto rest setting after game 2. The logic does not account for the off day when checking that. The next pitcher is decided immediately after the game. So, if Ducey was at, for example 75(100) after game 2, and his auto rest setting was above 75, he would be skipped as the next starter, even if he would have been at 100 after the off day.
If you want to do what you tried to do, you have to set the auto rest setting below what the pitcher will be at after game 2. For the playoffs, I usually set the auto rest setting for all my starters as low as possible and manage the rotation myself for this very reason.