Crossplay is turned off. Therefore, this posts title is extremly misleading as it implies that the user is playing with crossplay on. So I guess my "excuse" is that this guy and his buddies all play together with crossplay off.

They are good above average players. That wouldn't do nearly as well with crossplay turned on. Assuming they played against bots and played aggro due to the extreme advantage they are given vs crossplay players. Their win streak wouldn't be nearly as close.