@rich: True building passages where the way goes *through* (like many Soviet apartment blocks have around her) are indeed generally connected and this doesn't stop routing. This here isn't a building passage but a sky bridge. It's more similar to a bridge area - you wouldn't connect it there or you will end up connecting different layers - like a lower path to a bridge railing - this would break routing. So if one were to map something more than just a building wall/part, then such a connection would be problematic. It usually isn't and which is why I said it's "technically" incorrect, but practically fine for most cases. I left them connected here myself when adjusting the building part.