Steven, NC does not “cause” us to detach it is simply an act that lessens the blow when we are that stage of trauma - right after the break.
Rather than feverishly protecting NC – have you dug deep as to why you may be ruminating? What it is in you that is creating the hook?
We attach ourselves to a Borderline for a very good reason. That reason is not who your ex is but what she symbolizes.
I see why you are called "Clearmind".

I also am learning the answer to the OP's question is not all that simple and similar for most of us but certainly not the same. Many of us talk about the 'void' about having 'lost ourselves' and this is probably the single most valuable thing I have gained from the forum.
In 3 years since I pulled the plug on the engagement I have looked deeply into why I have this void in my life... . and in fairness it's not all about my exBPD but certainly is a large contributor towards it.
I will share this too... . I found a letter I had written to myself... . two months BEFORE i met my exBPD gf and the purpose of the 'letter' was to outline where i was and what i was feeling and what i wanted for my future. my kids were growing up, I had big success financially, I had an incredible life. In the letter I pondered choices I could make to change things up... .
My point is I was a prime 'target' at that exact point in time and I wrote that letter on a small island while on vacation... . Two months later a random woman from that same island reached out to me... . Talk about serendipity... . oh by the way... . (this is true) "Serendipity" was part of her online dating name.
Chills.