T-Shinzon, you are thinking too much about this.
Technically, you could kill the team off and cap before they respawn. But, you have to kill the other team to do that. And, you are faced with waiting until your energy is up high enough to cap.
As I recall, that paticular match was not very long.
I am in full agreement with you that Helltube is not the best map to scrim with, if you want to play XMP. In fact, I dislike Helltube personally. I don't care for any of the deathmatch maps that have found their way into the XMP world. But, as I said earlier, that is the map X chose, and we honored their choice.