Warbanks exist completely negating the separation of realms, nevermind the fact the AH is region wide, ie - all of Europe.
Looking at that article it’s trading gold between different versions of WoW, ie – player getting gold in Clasdic giving gold in Retail. Think there’s been too much scams.
As long as it is not a “service” guild then there is nothing to worry about.
tldr from their Q&A is that it is strictly about services. So if you are just a regular player that plays the game and occasionally helps your friends or offers to buy an item from a run, it is all ok.
The problem in their eyes is when your main activity is offer “services” for facilitating trading of gold/other items. They have not gone into details, but it is aimed for the big fishes.