They are and they aren't. Kingsville is a tiny-leafed variety of Buxus Microphylla (Japanese boxwood). They're not the same. Kingsville is a variety of Korean boxwood. Kingsville is a lot slower growing than the main variety (if in fact, you actually have a Kingsville--there are six or seven different varieties that are often confused with it because they have small leaves. Kingsville typically has the smallest among them, however.)
Kingsville push dense leaves, while the main variety may push more extension growth. That may lead to some trees in your forest to look a lot different from each other....P{robably won't make that much difference however