I don't imagine that it matters to Rowling, inasmuch as most (sane) authors (with bills to pay) would take the sales over the recognition. My frustration mirrors that of Michael Glitz: what is the point of a bestseller list if the publisher of the list decides which books belong on it? It seems like gerrymandering, to me, to pick and choose which genres are appropriate for the list, rather than looking quite literally at which books have sold the best in the given period.