I've been in very close matches (e.g. 91-98) where the spiral is the final decisive battle. In this situation, the team with the higher points going into the final spiral battle wins the beastmoon hunt, even if they lost the final spiral battle. I think this happens because their final points total is probably higher overall, or due to a glitch in the way the points are calculated. Either way, I feel the team who wins the final decisive battle should also win the hunt. Or, both teams crossing the 100 points threshold should be considered as winners (e.g. win points)
My thought would be that if both teams go over 100 on the final battle after all points are counted, the team with the higher total score wins the match. If the total score is tied, then the winner of the battle wins the match.
I've been on both ends of this, losing the match due to winning spiral and vice versa. It's certainly unfair, and even when I win due to this it feels a bit hollow. Like the last battle doesn't matter at all, just defeat enough enemies and sit there and you win regardless.