Will share this in case it helps. I had been NC with my dad since childhood in a very messy way, had some contact in young adulthood to after he got in touch with me over Friends Reunited, saw I had left home as I was working in a different city. At that time I wondered if it was worth trying again, as it had been 20 years.
There was no real apology, no taking responsibility for what he'd done, lots of trash talking about my mum (who had many faults and issues let's be clear, but he said some horrible things about her that he had no sense saying to any blood relation of hers). There was also a lot of tryign to force the same behaviours and patterns that had led to the breakdown of our realtionship when I was little.
So that was brief and I went NC again in full knowledge that the right thing had happened when I was child. It did underline in my mind that the door had to stay firmly closed.
When my mum died he got in touch again.
I reckon he got in touch with me after my mum died because he thought I would be vulnerable enough to be open to an approach (he had this idea that the NC was all my mum's fault, nothing to do with his behaviour and she had poisoned me against him). There was something really premeditated about how he did it, like he had been waiting to hear this news for while. That somehow waiting for my mum to die that was a better chance at reconciliation than saying sorry and making amends as soon as he could.
So he thought the coast was clear after she died. I'd didn't take him up on it. In fact, I found it was done so cynically that it hardened my resolve. prior to that, I had thought that if he'd gotten in touch at some point saying I only have a short while to live, I wouldn't have had the heart to refuse contact then. Now I would do so without hesitation.