They announced the change in voting at the start of the season. However, I fully believe in reality show trickery here. Don't really believe that the judges got to actually vote, but the decision was made before the show by the producers who then fed the judges their lines.
As proof, have you ever noticed that in this situation the first two voters will always split, leaving it up to the third voter to decide? Happens every time. If it was honest, half the time the result would be decided by the first two, making the third vote irrelevant.