He uses it in the same vein as 4chan, an insult to those he views as woke and guilty of operating under an ethical framework they never question.
Graham sees his pre gender criticism, left-leaning days as something to be ashamed of and describes himself as a former NPC, especially when talking about his involvement with Gamergate.
If you search his X feed for NPC, you can see him using the term again and again and again, usually coupled with an insult. These aren't unusual:
"Apologise to your mother you fucking NPC"* *
"You shut up, you fucking NPC nobody. Apologise to your mother."
He uses other 4chan / redpill terms now
"Jolyon Maugham is no normie. He's transed his daughter"
This doesn't make him inherently bad; it's just embarrassing that a man nearing sixty would use these terms, especially given the cultural pond they draw from.
People are within their rights to find that kind of behaviour a barrier to taking him seriously.
Anyway, you'd be insane to quibble over whether he uses the term NPC. Given how he uses it and other GG terminology he now has in this lexicon, it's a fair assumption he has some alignment with those red-pill dunces, and as to whether this makes him bad or dismissible? That's a matter of opinion; make up your own mind