If you’re going to implement a matchmaking system, there needs to be a fair and balanced mode that is able to determine a clear winner with one map play through. Making the game unnecessarily long because you have to play a map twice will turn a lot of people off.
Speculation time: A goal that they were aiming for during Mirage’s development was making the objectives more competitive. This included making them quicker. It’s not out of the question that the objectives in Chiv 2 could be significantly shorter than their Chiv 1 counterparts, which would allow for halftime switches to be more reasonable.