That was total BS. Congratulations for being a great team and working together through great obstacles when the other two teams completely fell apart under the same circumstances. Instead of just letting you split the money, like you would have if the other teams hadn't imploded, you're now going to fight each other for the prize.
I'm not sure why this aggravated me so much... the two "losers" didn't seem bothered by it at all. I really think it's wrong to change the rules in the last few hours of a competition like this. You start as a team and you should finish as a team.