Middle of the match connection
I interpreted this as a third or fourth player being able to jump into an already ongoing multiplayer match
If this is the case I could imagine it being a different type of "brawl" game mode, maybe like a constant match to see who can get the most dqs or decaps in one round or so? So like after you are dq'd you can respawn kind of thing that way if you join mid match it's a fluid match etc.