I'd think it'd be a little hard to add details like that to dirt roads. Especially considering that dirt path looks like its on secluded private property, you wouldn't want a texture with ruts and and horseprints on your secluded forest hideaway if that path never actually saw traffic from wheels and horses.
Having no idea how exactly they are programming the formation of dirt paths/roads, to me it seems like that at present (remember it's alpha) they are simply removing the "grass" overlay texture on where they designate their paths (whether that system is manual or automated is anybody's guess. Have they said anything about path formation being automated triggered by frequent traffic?) and revealing the bare terrain texture beneath.Perhaps eventually they'll add a traffic marked overlay to their dirt paths/roads further down the track.