Can MLS really do curved?
Yes. Within the service area, MLS allows the aircraft to determine 3D position with very high accuracy & precision. The onboard FMS can then compute curved trajectories between waypoints -- including curved glide slopes if desired. The FMS database would contain all the information required to construct each curved segment (e.g., center of the turn circle, arc length of the turn, radius of the turn, etc)
In principle this is not very different from a GPS approach.