Strange you should notice this as most Australian's I know find the South African accent the most unlikeable together with the New Zealand accent. The two aforementioned, to be the most confused with each other and disliked in my circle.

Welcome Cathryn, always nice to have another West Islander join us. While transtasman rivalry goes a long way to explaining why NZers and Australians generally dislike the accent from the other side of the ditch, no NZer that I know would ever confuse an Australian accent with a South African accent. Given that the NZ and Australian are quite similar when listened to with an objective ear, it is surprising that your circle of associates could confuse NZ and Sth African. Like most Kiwis, I find a pronounced Aussie accent to be quite grating, but also unmistakably Ocker. I guess that to outsiders, Ausies and Kiwis are "two peoples separated by a common accent."