This may be something to do with married fares that I cannot understand but I could not find a recent thread to post the question in.

I was looking to fly CGK-DUD and in the recent past this was not offered by Air NZ. However it is now being sold, and starts at $1062 and involves:

CGK-SIN on SQ
SIN-AKL on NZ
AKL-DUD on NZ

I have been making a habit of searching for the same fares for AKL to see how much I'm being charged for the domestic add-on, and found a bunch of fares starting at $899 for CGK-AKL. However instead of going through SIN on SQ, they instead go

CGK-DPS on GA
DPS-AKL on NZ

What's going on here and why can't I access the cheaper flights through DPS/AKL? NZ291 arrives early in the morning and can connect to any number of domestic flights AKL-DUD.

CGK-DUD fares at $1062 were few and far between but there was widespread availability for the same period for CGK-AKL at $899.

When I checked, PVG, SIN, and HKG flights were all only +$80 when flying from/to DUD instead of AKL, adding to the pain of the situation above.