More or less there isnt a rule, but there is a conflict of interest, where it needs to determine whether or not the job is genuine and whether or not this position was created for the purpose of allowing you to migrate to New Zealand.
I do not beleive they are discriminating against you in anyway unless you truely have skills or qualifications in which your position is essential and cannot be filled by NZL residents.
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IAA Registration: 200900293