I recently read a (non-fiction) book where exactly that kind of clustering was talked about. It's correct that you'll find clusters in each major continent, but with just 6 clusters one of them will be entirely devoted to a small, insular community in the north of Iran. To your eyes and our social consciousness this community would be considered "middle-eastern" when in reality they're about as genetically as different as "Black people" and "Asian people" are.