I mean, it says cybertruck parts, not the whole thing including assembly. Certainly possible for some manufacturing processes under given conditions to produce parts with ±0.005 tolerances like laser cutting or precision CNC machining of small dimensions. But it's obviously completely unrealistic given that most parts for a car will be of large-ish dimensions and stamped, injection molded, cast, forged, extruded... none of which lends itself to IT grades better than 10, far away from talking about microns.

Musk is a scammer who has almost no practical understanding of engineering.

He (and unfortunately many after him) forgot about thermal expansion and contraction as well with his dumbass Hyperloop idea. Have a hermetically sealed metal tube with a vacuum run exposed for 200km and let's just ignore thermal expansion. One station would have to move left and right for several meters throughout the day, every day for that, the 200km pipe somehow would need to be able to move about... His "designs" and "ideas" are engineering nightmares

Nah, not impossible people build stellarator type Fusion reactors with large freeform metal parts in that tolerance region that are exposed to liquid helium.

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.