The functionality for "Alliance Victory," an option you select in the lobby setup, does nothing. Whether or not you select "Alliance Victory" it will still allow alliance victory, meaning everyone alive in the game can ally each other and win the game, thus, more than one person can claim victory. If I interpret the setting correctly, it should not allow people to win that are still allied with another player. This ought to be a simpler fix as this was a function within the game before, and it was removed. I was very happy to see it back once I returned to the game but it is unfortunately useless at the moment, and I hope to see it fixed soon. Thanks for your time.
A year and then some later this bug is not yet fixed. It seems like it would be a simple change of some conditional in the code, and it breaks an entire option of FFA Alliance play if you don't want more than 1 person to win.