It doesn't seem that wrong to me. The AA office for AU and NZ is now in AU. If the tickets are being issued from the office, then could reasonably expect them to say that they cannot issue at NZ prices since they are not in NZ.

They are able to do them but seemingly have put in a restriction to help to ensure that the sales restriction is not circumvented by someone in Brisbane phoning the office in Brisbane and avoiding paying the AU price.

SWP is not the only region where using foreign credit cards are restricted; AA US ,won't take non-US cards in general

The issue can, I would expect, be circumvented by using a travel agent in NZ , ensuring that the 1st sector is on AA flight number and having the agent issue it through AA

Dave