I can't give any specific ruling to it but that's the way it has always been since the one way was implimented. But here's my take on it. The one way is in effect due to restricted visibility on steep hills where vehicles coming from opposite directions can hit at the top. If you are still on the north side of the hill, there is no restricted visibility.
Note; even the guided dune rides do it.
GLFWDA member since 1979.
Member Southern Michigan Rock Crawlers.