The diagnostic criteria for NPD include “Interpersonally exploitive behavior”, which doesn’t describe a symptom of an illness, but an effect on others. This is bad psychology. Psychologists are doctors, not priests. Morality is not medicine. The responsibility of a doctor is to help a patient, not judge them. The DSM’s entry on NPD is bad. And many experts agree on this, because even the inclusion of the disorder in the fifth edition was controversial.

https://link.springer.com/article/10.1007/s11920-009-0084-z

The diagnosis of narcissistic personality disorder in the DSM-IV has been criticized foremost for its limitations in capturing the range and complexity of narcissistic pathology. The attention to the narcissistic individual’s external, symptomatic, or social interpersonal patterns—at the expense of his or her internal complexity and individual suffering—has also added to the diagnosis’ low clinical utility and limited guidance for treatment. Recent studies and reviews have pointed to the need for change in the diagnostic approach to and formulation of narcissism.

There’s no point making an appeal to authority when the authorities are in such disagreement about the fundamentals of NPD. It’s better to listen to actual pwNPD with lived experience.