It makes sense when looking at the nature of the bond and why staying in the relationship becomes a matter of life or death. Because as a narcissist it is literally like you are loosing a limb because by definition these people have become an extension of ourselves.
This also helps explain why and how we get sucked into the intense neediness and love bombing at the beginning.
It sounds like you are making great progress in therapy - and have a good therapist.
I think your point is right on the money for many of us - what makes these relationships painful is how we are processing our side of it. And the narcissist/borderline paring is very common. Have you seen this book -
https://bpdfamily.com/message_board/index.php?topic=56788.0So having thought I was the 'lonely understanding co-dependent child' I'm having doubts.
Past relationships and behavioural patterns- paranoia eating disorders and treating 'nice' girls badly etc have forced me to look at this relationship from a different angle.
Have you taken this test?
https://bpdfamily.com/message_board/index.php?topic=202548.0