In my opinion I guess it would depend on the situation and the person you are going NC with. My ex-husband was such a piece of excrement I had no problem not informing him of my choice to go NC.
If it ever comes to the point where I want to leave the ABF, well, I would tell him, because he's never been abusive to me. He treats me 180% better than my ex-husband ever did despite his alcoholism, so for that I feel I would owe him at least a reason why.