Well, they apparently decided they didn't want any situations where the last of the five sets was a dead rubber, as it often is in Fed Cup or Davis Cup, where one team already has three victories and it doesn't matter who wins the fifth.
So it is set up in WTT that if the team trailing wins the fifth set, it goes to overtime. In over time, the trailing team must win every game until it catches up. If the leading team wins even one game, its all over, as it was in this match up between the Sportimes and the Breakers. Delgado won three games in a row for the Breakers, but then Morrison won one game for the Sportimes and so they won the championship.
But if the trailing team catches up, they go into super over time. Not sure if that is just playing another game, or it is a five point tie-breaker