I believe a number of the Qantas A330s were delivered nonstop from Toulouse to Sydney. Also during the 1993 Paris Air Show an A340 departed the show, flew nonstop eastbound to Auckland, New Zealand, refuelled and carried on eastbound back to Paris, arriving just over 48 hours later, including the stop, so just under 24 hours each leg. Obviously going with the prevailing winds throughout.
I don't know whether your 21hr 10min for Sydney is eastbound or westbound, but I would expect it to take almost 2 hours more westbound than eastbound. Unlike Auckland, Sydney is sufficiently short of being halfway round the world that it wouldn't be worth carrying on eastwards.