Yeah... that's just how it is. The penalty that you avoid is not being able to queue because leaver. It doesn't say the game isn't going to count. Is it stupid beyond reproach? Yes. But it has been like that since forever. So yes, if one person leaves the entire team gets punished with a loss, unless you win 5v6 which doesn't happen unless game has been going on for ~20min and objectives are at least even.
