I'm not questioning your story, but for my own part (5 or 6 trips) I've always had neutral or pleasant interactions at AKL. There are only two that are even memorable:
On one occasion a quarantine officer scrutinized some raw wooden Christmas tree ornaments and called her colleague over - - - to admire how cute they were. "No problem, ma'am, have a good day."
On another, the immigration officer asked why I was visiting (for 3 days) and I launched into an enthusiastic description of my research project. He cut me off mid-sentence and waved me through.
While it's not odd for Australians to go to NZ for 3 days (lots of people go for a weekend break), it shouldn't be odd for people travelling between the US and Australia to take a short break in NZ either. So again, I'm not disputing your experience but I think it's not the norm.