You're forgetting there are also 3 other flights ex-AKL to DXB. The nonstop service frees up space on the flights via Australia for higher yielding passengers ex-Australia.
Far from it, ANY competent revenue manager prices that into ticket prices for onward travel.
The direct AKL flight competes primarily with CX, SA and NZ on one stop services to the EU/UK, it was never put in place to free up capacity or yield for east coast traffic out of Oz, the numbers have always shown that the vast majority of Y and J class pax on EK ex AKL stop in Oz.