In my experience, SQ 231 is always the shortest SIN - SYD flight. Most of the time, the flight path took it directly to Jakarta instead of over Bali and heading down south coast of Java to Christmas Island then Port Hedland before turning towards SYD.

So, don't be surprised if you will still be arriving at around 10:05 SYD time.

All other SQ flights to SYD however are always taking 7 - 7:25 hr.