The red part is the linkage as show in post #1. The end of the linkage is covered by this knob:
The only function of the knob and linkage is LOCK the door, by pushing it down. Once it is pushed down nearly the whole knob is within the door trim, making it impossible by unlocking the door using a wire to hook it up.
The door can be unlock by the external door handle. Or by pulling the internal door handle, which is the green part. All the motor mechanism for locking/unlocking is behind the door panel, in a sealed assembly.
Of course the linkage moves up and down during locking and unlocking. But the only moving part that comes into contact with something is the door knob. The screw thread at the end of the linkage rob is nearly complete enclosed by the knob. The screw thread does not come into contact with anything during locking and unlocking.
The question is why half of the screw thread end of the linkage rob is machined away?