As its an public dungeon its not instanced but else you are correct, same is done in Summerset and Elsweyr as in the public dungeon is overland in practice. Yes its other public dungeons who is overland like the one in the Rift, even trials like Hell Ra but they don't take up map space so its an way to pad the map.That's the Underweave (Apocrypha Public Dungeon), its instanced map layout matches with the one seen on the Apocrypha zone map.