Highlighted the important part you overlooked.
From the original blue post:
Organizations operating across multiple realms and excessively advertising non-traditional in-game sales are contrary to the terms and conditions of the Blizzard End-User License Agreement (EULA).
This policy update does not restrict individuals or guilds from using the provided in-game tools (“trade channel” chat) to buy or sell in-game items or activities for in-game currency. However, “boosting communities”, especially those who operate across multiple realms, are no longer permitted.
We urge all such organizations to cease doing business in World of Warcraft immediately, in order to maintain uninterrupted access to the game.