If I were the one asking the questions then I would throw in the free door to get the person to reconsider their first choice. By the way you are chosing then I would always have the upper hand. Therefore I always stay with my first choice as it is most likely right.
Remember that if you have a 67% chance of chosing the right door then you also have a 67% chance of chosing the wrong one. Optimist of pesimist your choice.
