A wrist joint that rotated independently of the arm first started with the OR156cm dolls. I think over time, the factory have realised it's not such a good idea and have gone back to the old design (or an improved design). I've confirmed this now on OR 156cm, YL 160cm and WM 170cm. To me it seems a much better way and maybe there's a case to say that millions of years of evolution have it right.
Do you like it or would you prefer it the old way?