What is the purpose of giving this Generic Outcome ?
INZ can only act within the bounds of what their purpose is, as set down in the regulations.
http://www.nzqa.govt.nz/assets/quali.../guide-IQA.pdf p.21
Q. What is the purpose of an International Qualification Assessment?
An International Qualification Assessment states, where possible, which currently offered New Zealand qualification(s) on the Register of Quality Assured Qualifications (the Register) are substantially similar to the qualification(s) you have gained outside New Zealand. The International Qualification Assessment also indicates the level of learning outcome your qualification represents on the Register.
Q. What does it mean for me if you cannot find a qualification available in New Zealand comparable to my qualification from overseas?
If it is not possible to specify a particular qualification currently offered by a New Zealand qualification on the Register, because there is not a substantially similar qualification to one or more of your nominated qualifications offered in New Zealand, the nominated qualification will be compared to a level (and where possible credit value) on the Register.
If an international qualification can not be compared to any New Zealand qualification because the NZQA was unable to determine the accreditation status or authenticity of one or more of your qualifications, this is stated on the International Qualification Assessment report.
(my bolding)
They have to look for something with substantially
the same content, if they are to name one. If at the moment there is no degree giving the same content being taught in NZ, there is nothing they can name. This is no insult to your degree. They recognize its level. You could ask for a review (see p. 22 of that document), asking if it is possible to align it with the description you need, but in your place, so as not to waste time and money if things genuinely are very different, in NZ, or since you studied., I would first do some research to see if you can find a current NZ university syllabus which appears to you to cover the same material as your course did.