If interested, the piece has a link that goes in depth on what narcissism is. Specifically, this is in the fourth paragraph, which links to the words ‘dark side’, with a 23 page article.
This also reads like a complaint. I don’t see anything in that definition that distinguishes it from other dark triad personalities.
But I have been looking into this a lot, and I think the way to understand it is as an intense insecurity. Maybe about something that was their key to receiving acceptance and affection as children. These are people in pain; they don’t see yours. It is the most benign of the dark triad in that the others begin deliberate manipulation and harm.