Boy, I was definitely the recipient of the ignore treatment by my ex-N BF.
I strongly believe that ignoring people is a form of emotional abuse. It's a tool employed by those that feel out of control and weak. They do it hoping you will continue to contact them over and over, as it makes them feel powerful, and proves their worth and desirability.
It's pretty effed up, IMO. As I have met only one person as an adult who has ever done this to me.
I begged my narc to meet me when we split, as I wanted to have a closure talk, clear the air, and wish him well. He ignored every request I sent. I know now it only fed him in that sick way he gets off on. Sad, really.
I think a real narc replaces a GF with any of the back burner women he has ready to go, as I don't believe a narc ever fully invests in just one person at a time. It would be far too dangerous. Normal people suffer breakups. Narcs would never expose themselves to such a situation. Because of course, they don't HAVE to, right?