This you can do anyway. So using it as a counter-argument is naive.
nay it is not naive. if you know when someone will go inactive/gets booted from the round players that are invited usually take place seldom is it rare to see a random player join. having manual removal lessens the chances of replacement cheaters. it is known that the devs placed a join limit to games to prevent late game joiners on the grounds to give a player a unfair advantage. Also players didn't like the fact that their former ally being booted and replaced by a random player and attacks them from within due to the right of way.