New Zealand was colonised long after castles had become obsolete. There are a few remains of WWII coastal fortifications here and there, but they’re now obsolete too.

The Māori built thousands of hilltop fortifications with wooden palisades (Pā), but lacking metal tools they didn’t build with stone.

See, I'd class those as something like 'follies' or Whimsy, as they don't appear to be actual fortifications, rather forms of affectation.

That said, I'm not sure what definition or list this site uses - as others have already pointed out, there are loads of castle missing I can tell, just from a few that I've visited across Italy.

The page does give a pointer to Wikidata, I for one would love to see your example included.