Excellent article, very concise too. I enjoyed it. I especially agree with the importance of clarifying whether you KNOW someone has the disorder, OR you're just using "narcissistic" the adjective.

Allow me to add to your reasoning a bit: sometimes (Idk how often, I don't have stats, but I see it often enough), a single author can write a lot about narcissism simply because they were victims since an early age. It is my case, and also the case with many people I read from. Former victims of narcissistic abuse tend to get into relationships, friendships etc with OTHER narcissistic people (possibly NPD, or very close to that if not full-blown NPD) simply because of that good old trauma bond and sense of familiarity that our subconscious picks up on.

This is not to disagree with what you said at all, I'm merely adding something more to it. I speak from the perspective of a survivor whose stories other people often don't believe because they're always "more of the same" and can sound like paranoia around narcissism - when in fact it's very plausible that a lot of people in my life are indeed narcissistic, and psychology explains that.