Why is the direct Sydney to Osaka flight unavailable but indirect flight from Cairns available?

I am trying to book a flight from Sydney to Osaka in December. I can’t get a business class flight when I search SYD-KIX but when I search CNS-KIX there are seats available with the domestic connections taking me to sydney then QF 33 direct to KIX. I don’t need the flights from CNS-BRIS-SYD. Can I call Qantas to book the SYD-KIX flight only as I live in Sydney.

is this for paid or rewards booking? Calling makes no difference, if it’s not available online.

It is for a reward booking. I called qantas FF and they told me I would have to fly to cairns to start my journey or the flight would be recorded as a " no show" and cancelled. I asked why the SYD-KIX leg does not show up when searching for flights from SYD and was told this is to allow FF members in other towns to get flights. Guess I will have to look at other options.