Hello Pottu, I was one of the members of the Alliance premade in that screenshot that has been going around recently:
Me and Letholdus were the 2 Americans in the alliance premade who were nice enough to be given an invite. We had already faced this particular horde premade a couple times in the day, and this horde grp was the only grp we could not beat at blacksmith with our very skilled paladin lineup *wink*. Because this was our 3th or 4th time against this premade, and we had already been forced to 2 or 3 cap a game against them already if i do recall, we ran all 15 people to BS to try to see if we could wipe them and failed, so instead of wasting everyones time, we were told to give up, and underneath the scoreboard theres myself RP walking with my Sulfuras out. This is pretty normal for premades to do I was told, tho I dont have much experience in them. I think it can hardly be called win-trading if we can't even take an easy game off the other premade we are supposedly win-trading with lol. Not to mention, I highly doubt a bunch of rank 13s are going to put their ranks on the line after PvPing legitimately for weeks. Both myself and Letholdus were legitimately surprised that players in either premade were banned after we duked it out for several games; often we have slight suspicions of malicious activity but that is just silly drama-seeking at best as the legitimacy of our premade was proven to us as we continued to play. I think that if the Chinese premades truly wanted to wintrade, they would not compromise themselves by inviting two North American players, its that simple. If you have questions for me that I can answer to help clear anybody pm Tsirup on discord or ingame.
EDIT:Nevermind lol i did not heard about what happened in the Chinese chat channels, RIP about that