My first thought was along the lines of what Superdad said. Didn't the reshuffle help you, rather than hurt you?
Without playing the Cellar, you would have had only one Copper that turn, and after the turn you would have discarded and then shuffled. The three Estates and one Copper would have gone into your draw pile, or into your next hand.
After you played the Cellar, you had two Coppers, and after the turn, two Estates, two Coppers and a Cellar went into your discard pile while the rest of your cards went to your hand or your draw pile. By turn 11, most of your cards should have been better than two Estates, two Coppers and a Cellar, so you improved your next turn (at least), while (very slightly) improving your current turn.
That's how I'm reading it, but I'm probably just missing something. Feel free to point out the flaw in my logic.