I think in the jury house, once you are away from the game and decompress from the game, the people start talking and comparing notes and those things said in good bye messages will come back to haunt the people still in the house.
For example, if Andy hadn't told Amanda about the alliance, she probably would have continued to believe that Ellissa voted her out. That would have gotten him a vote at the end. Not sure his admission will get him anything, in fact it will probably come out that he was playing all sides of the house the entire time and that won't go over well.