Tbh, the sat nav system knows as much as we do when we look at a road on a map. Its a road.
At the very most it tells you how high it is or if its on an edge. It doesnt tell you what it is suitable for. It is down to people teeling the sat nav comapnies to update their mapping database to know what routes are not suitable.
If your local and know a better route, just ignore the sat nav and let it work out where you are going.
Still funny though...