I apparently missed the claim of 18 frames of brood in a colony. I have seen hives with brood in 18 frames but I have never seen a single queen able to maintain egg laying in 18 full frames of brood, it would surely take a second queen or resources from another hive. But that issue aside I just don't get what mechanism allows greater brood production without a corresponding increase in mite populations. In my mind the ideal hive that would be able to control varroa of its own devices would have to be highly Hygenic (constantly reducing bee population) and have a shortened laying season.