Exactly, people forget that the critical criteria for diagnosis is whether the cognitive features prevent the individual from achieving his personal goals in life, or cause problems from those around him. And indeed, as the article says, schizoid individuals have significantly reduced quality of life and some of the lowest scores of life success among personality disorders. Without this, there would be no basis for diagnosis.

Yes, exactly. Those questions are determined by interactions between the patient and the provider, which is inherently subjective and therefore flawed.