I don't necessarily agree. The NRL is a professional sporting competition which is based in and run by Australia. It's not an international test. Not everyone in the Warriors side is a New Zealander either.
Whilst the HQ of the NRL maybe in Australia, the competition itself is not "run by Australia", fairly sure that would make Julia Gillard the ultimate boss, which might be a problem.
Our competition is actually an international competition with two nations presently having representation and with the possibility of more in the future.
By your logic, it could also be said that the competition is 'run by NSW' by virtue of it having its HQ in Sydney and the majority of clubs in NSW.
In the last ten years it is unlikely that there would have been a Grandfinal that was a hundred percent Australian, so by your logic we shouldn't play the Aussie Anthem.
Play the Anthem of NZ and Australia because this game is about two clubs that represent areas in two nations.
And I can't wait for the Kiwi Haka in the stands as we have seen in the last couple Warriors games.