I just (at the time of booking) managed to get 2 x JL business reward seats from NRT to MEL direct for November this year, in November last year (yes, booked 1 year in advance).
Not even a school holiday period nor a peak period (ie. cherry blossom season in Japan), but it was already hard to find.
Before securing said seats, we procrastinated and lost out on business reward seats departing the week prior - so I kept looking daily and when I finally saw some newly released seats departing a week later (what we have now), I jumped on them and booked immediately.
If you're looking for seats now for 09/2024 this year, you're probably 5 months too late unfortunately. Looking for just 1 adult now for September this year yields almost zero reward availability even for economy.
Who knows though, Qantas may have more availability randomly - you'll just have to keep looking and also be flexible / be open to transits (ie. through Singapore / HK or Taipei etc).
Instead of searching for MEL > NRT, you may have to try a different combination of the below examples:
MEL > SIN, then SIN > NRT
MEL > HKG, then HKG> NRT
MEL > TPE, then TPE > NRT
Or even try from SYD.