Much of it, at that level, is a mostly arbitrary construct, with blurry boundaries, left to subjective interpretation, made up long before the very new concept

Much of it, at that level, is a mostly arbitrary construct, with blurry boundaries, left to subjective interpretation, made up long before the very new concept of genetic analysis was even a thing, where a more informed hierarchy could be made. Even then, the end bits of the hierarchy turn into a knotted mess a generation or two after you remove a river or mountain. Categorization is a fundamental part of our intelligence, but not necessarily a reflection of reality.