i remember when 7 people from my server was also in the same bg and i got a whisper from the other team to KYS for playing premade. i wasnt even in the group…
They queue at the same time and only accept the queue if all their groups get the invite at the same time. Often they even go mercenary for faster queues.
The Russians originated this method of having fun in WoW, and because of their server segregation from the rest of EU it was much easier to exploit the system, but now with communities the rest of EU has joined in in the fun and are also forcing very large premades into random BGs to clobber randoms.
It’s one of the most toxic and cancerous loopholes that Blizzard has ever allowed. It’s very indicative and symbolic of the status of the game and company as a whole.