Pivot points remain roughly in the same location whether it be K-Line, Lionel or William's. Placement of the blind driver mid truck doesn't restrict the swing or the ability to negotiate 031 curves. The inherent lateral free play in tinplate type wheel sets prevents binding on flanges. The same geometry allows steam locos with 6 or 8 drivers to traverse the same tight curves, as long as the middle drivers are blind. LionMaster articulated engines can handle 031 for the same reason and look extremely awkward doing it.