You are correct in that there is little to no Greyhawk content in this article. That is because this article is a companion piece. As such, the point of it is not so much as to specifically present additional Greyhawk material as it is to complement the previous articles posted regarding witches, in particular "The Witch" character class article. Keep an eye out for a more comprehensive article on "The Coven", its history, and its involvement in the World of Greyhawk.