I find it easier to book JNB-SYD in J as an award then most US cities-SYD. Just recently booked a RT J for 160k JNB-SYD via KLM/CZ one way and MU/CZ/AF the other. Of course even with this you have to be careful with. It'll show lots of 80k options (which is of course the only level available since it's going to be all partner metal routing) but a lot of time one of the segments is in Y instead of J.