When so many of the local populace being permanent residents and dual nationals then you can only describe this is as a government bureaucrat job scheme. I can't imagine Sabre or Amadeus going to do a mountain of development to register a separate identity document for travel to allow passengers would are NZ nationals or those with residency visas to pay a different fare, let alone a aggregator like TriVago or Expedia to change their interface to facilitate exemptions in airfares.
I can't see booths at arrivals and departures with passengers queuing up to show they paid the $25 levy, then processing their ID documents and handing out $25 in cash, credit card refunds or international bank transfers being part of a seamless visitor experience or streamlining the chaos at Auckland Airport when a bunch of inbound aircraft arrive at peak times - I can only assume that they will have to exempt Australians because they don't give them a residency visa or alternatively we'll all be queuing up to pay $25 entry arriving in Australia as kiwis in a tit-for-tat with the Turnbull Government.
The alternative is paper or online forms, scanned documents and refund processing and another wing of Internal Affairs.... or they say exemptions are too hard and we all get paddled an Sir Apirana Ngata everytime we head to Australia - $25 for NZ and $25 for Oz because anything we do to Australian citizens will be matched here and the NZ Labour led Government and the Australian Government are getting along so well.