He's a kiwi that sounds like a kiwi. What part of that is remarkable?
From what I've seen people who have moved to NZ after the age of 16 keep their accents (more or less), before that age they lose them. You can live in NZ for 30 years but if your first 16 years were somewhere else that's the accent you will keep.
Look at Ernie Merrick - moved to Aus around the age of 20 and spent 40 odd years there. Doesn't sound like an Ausy to me.