I don't disagree with you on any of those points. In this instance, in addition to DEM, it shows up on USGS maps and the Strava Global Heatmap. I try to verify something via 2-3 different sources before adding. (some combination of USFS, USGS, DEM, aerial imagery, Strava, trail maps, VT highway maps) If something exists and people are attempting to navigate it, I think it warrants adding to the map. And I don't think track is exclusive for vehicular traffic, hence the existence of the smoothness=impassable combo. I've run on many old 'track' roads in New England. Some are wide enough to drive a truck down and have stone walls on either side. They also includes 5 ft ditches in the road where snow melt annually creates a running stream. Per osm guidelines, my interpretation is that since this was originally constructed as a road, it should be tagged as such, regardless of it's use solely as a path by hikers and stubborn mtbers. 

That said, I added it as generically as I could and always invite others to add appropriate details where armchair mapping fails. Since people are attempting to use this, (even before it showed up on the map), deleting does not seem appropriate. 