> Couldn't help noticing the video appears to show the demo car also has 4WS with rear wheels also steering
First thing I noticed as well. I would imagine it's also possible without it, but you'd likely be losing traction on the rear inside wheel? At slow speeds some cars already do this anyway, even with the differential helping minimize it.
BMW has that on many models, rear wheel steering and variable-ratio at the front. It's an option they call Integral Active Steering. The rear is steered either against or with the front, so it will make a tighter turn on a parking lot and it will "crab" on the highway for extra comfort when changing lanes.
The front ratio uses a planetary gear set to give you a higher or lower steering-ratio based on speed, and it allows the stability control to automatically counter-steer a bit when loosing traction at the rear.
First thing I noticed as well. I would imagine it's also possible without it, but you'd likely be losing traction on the rear inside wheel? At slow speeds some cars already do this anyway, even with the differential helping minimize it.