As someone who works in submissions at a literary agency, I would say that this is not a super important point in your query letter. From the book summary, we can basically decide what genre it is (as opposed to what genre people think it is, which is often very different) and more importantly, whether we’re looking for that kind of story. The only real issue is when someone is writing a memoir-type book or a historical narrative piece and we can’t tell if it’s fiction or not.
As someone who works in submissions at a literary agency, I would say that this is not a super important point in your query letter. From the book summary, we can basically decide what genre it is (as opposed to what genre people think it is, which is often very different) and more importantly, whether we’re looking for that kind of story. The only real issue is when someone is writing a memoir-type book or a historical narrative piece and we can’t tell if it’s fiction or not.