I believe when Young Peoples Week was being shown during the marathon, they went to the 4-4-1 setup. (Either that or 4-4-3, I can't remember) I think they did the original change in order to speed up the game and you could get a full game (at least, including bonus round) into 30 minutes, especially since Bill's pace wasn't as speedy as Bob's. When they found they were getting a lot in, they probably went back.
Interestingly enough, with the 4-4-3 setup, if you were to get all 11 questions in your favor, change the base card each time, and run the board while screwing up on the last card (with the exception of sudden death in one of the first two so you could get to the tiebreaker), you would go through all 52 cards exactly. This proves that the reasoning for the change in questioning was not because there weren't enough cards in the deck.
