For what it's worth, the NZ/TN codeshare agreement appears to have been cancelled, according to Wingtips 5443:

Suspension of NZ/TN codeshare services Air New Zealand wishes to advise that the block codeshare between Air New Zealand and Air Tahiti Nui has been suspended until further notice, effective from 25 Mar 2023. Customers travelling on/after 26 Mar 2023 on NZ314/315 will be re-accommodated onto the closest available NZ-operated flight (NZ902/903). Schedule changes will be progressively rolled out to your GDS from Monday and PNRs will be updated with a TK/UN status. Please ensure you check your queues for impacted bookings, contact your customers to discuss their options, and update bookings as soon as possible. Customers have flexibility as per the long-term Schedule Change policy.