Where do you get this from? As far as I can see the term "nationality" isn't defined in the statute (I may have missed this though), so his nationality could be considered to be NZ since he is a citizen here and has a passport
If that was the case, sections 6 and 7 would be redundant. Permanent nationality is the one acquired at birth.
I agree that's what they intended but it is very surprising that there's no definition for 'permanent nationality' in the Definitions of the Statutes. 'Permanent Nationality' has the potential to be interpreted as any nationality you have, as once you have the nationality it is often permanent from that time.
'Primary' or 'First' nationality would be much clearer IMO.