My interpretation of the rule is you could do JNB-SYD(transit)-PER-SYD-AKL-MEL-LAX.
ie the two transcon flights which would otherwise not be permitted are permitted if you are flying from JNB to PER with a transfer in SYD. Doing JNB-SYD(transfer)-AKL-SYD-PER-SYD would not be permitted as you are not flying JNB-PER with a transfer in SYD.
The exact wording of the exception is listed in the current fare rules on www.travel.com.au