Didn’t expect this. Just got an email from Sky:
"From 18 September 2019, TVNZ DUKE will be available in HD to all Sky customers. As a result, on the 18 September 2019, any future bookings, including “Series Linked” programmes, on TVNZ DUKE will need to be deleted and rebooked. This applies to bookings on TVNZ DUKE only."
Cool, will finally be able to record it in HD, or not have to swap to Freeview signal for live.