I think the idea of them missing something that is not with them is rational. Not sure it always applies. I think my H did not miss me at all. And, frankly, I didn't miss him much either. I missed the old H, and I mourned that for a month or 2, pretty seriously, but now (and I'm not saying this to be callous), I'm not sure there's much I miss. Mostly b/c the alien is most recent in my memory.
Mostly, I think for me, if I thought of NC in any relation to H's MLC, it was to remove myself from the equation in his mind: Always = Miserable Life For Me.
I wanted to comepltely cut myself from his life, such that he was faced only with himself, his actions and the consequences if any. I was sick of being blamed for everything, for feeling demonized. Sure, I had my faults and was demanding and critical at times, but I never made H feel that my life was miserable and unlivable because of him.
You know, like every other classic MLC story, his life tanked after I left. And I don't say that ot pat myself on the back. Simply that they are left with themselves....like the saying "wherever you go, there you are."
Also, it was nice to unwind from the drama that unfolded after I left. It was nice to take a sideline seat to his horror show of a life. And, in parallel, create a wonderful one of my own.