If you can even get something like +/-3 or 4 mm with say a cpk of 1,33 you are doing pretty well for a whole body.
It’s probably a pr stunt. If this is real then they are doomed because they have not yet understood that you need to compensate tolerances and design a robust assembly that can handle this. If you are trying to get crazy high part precision you have not understood how big scale manufacturing works. This is why the Japanese are often so highly regarded in this and might be the true art of car (or large scale) engineering.