That's not just a New Zealand phenomenon, and not just with browns. I was fishing a favorite hike-in brook trout pond last year and found fish cruising a lee shoreline sipping caddis flies. After taking 3 or 4 fish on a small caddis pattern, I spotted a larger trout porpoising out of the water.
A dozen casts and three fly changes later the fish was still rising--big splashy rises where the fish would rise vertically until its whole length was out of the water and then crash down on its side--and steadfastly refusing my offerings. I finally gave up fishing to it and just snuck the canoe close enough to see what it was chasing, and saw the damn fish snag a damsel in mid air, then do the same thing again. I never found a fly that would get a look. I tried a couple of damsel patterns I use for bass, but this fish did NOT want a damsel fly sitting on the water. It wanted one hovering about 4 inches above the water.
I eventually left the trout still rising, because there were other fish to catch, and they were still taking the caddis flies. They were all a lot smaller.