Until very recently, UA releasing J availability (USA-AUS) via Velocity has been exceptionally consistent T7-14.
To the point where I was able to book my wife UA J LAX-SYD with 2 days notice, only last month.
I’ve just done a search LAX/SFO-SYD/MEL/BNE, and there’s literally nothing T7 - something might be up.
Conversely, BNE/SYD/MEL-USA on UA availability close in seems normal.