I think airnz would have released more J award space because their bookings are light to the US. Also maybe it is in response to QF appearing to be releasing more premium award space from SYD/MEL/BNE to the US. Fiji airways also seem to be releasing more premium cabin space to the US than they used to, as well. I don’t really think the price in points to get one of those J award spaces via UA is exactly cheap. You might as well just buy a PE seat with NZ when on special and use RU or upgrades.