My ten cents:
I think things put in print can become very polarised. I've fallen foul of this myself on a number of occasions where the context and emphasis get lost.
Its entirely possible that the interviewer asked a very specific question about the break up and Nick gave an honest answer that, in his angle, Neil would from time to time, when disagreements ensued, mention that he could just break up the band if he wanted to.
Its entirely possible that Nick IS over it, that it doesn't bother him, but he's just telling it like it was. No different to me talking to friends about arguments I had with ex-partners, for example. It doesn't mean I'm not over it, in fact, possibly the opposite: I'm over it and I can talk about it...