I'm told it depends on your insurance company.... but there is absolutely nothing in my policy that says I'm not covered if I'm not on an "official" road. If that was the case you wouldn't be covered on some subdivision streets, parking lots, your laneway etc.
..and that video is hillarious (not for the owner). Pull the truck out upside down... and then break it in half using the skidder. Watched all parts of that last week.