Nothing wrong with those threads - thar is a mechanical interefeence locking thread design and built that way. Note the base diameter gets LARGER with more nut engangement - thread wear would make it smaller.
NOTE: It is CRITICAL to use only a free-spinning threaded nut and NOT a mechanical locking nut on that type of stud. If you use a locking thread (mechanical deformation of the nut) stud with a locking nut, as they will never come apart.