Well I played the risky game of booking separate itineraries
Today's QF12 landed at 06:13 vs scheduled 06:35. But can be the other way.
QF12 recent history. Includes a cancellation and delays-->
https://www.sydney-airport.net/syd-flight-arrival/QF12
Plus/minus 15 minutes of scheduled is considered "on time"
A lot of international flights arrive early morning
Link-->
https://www.sydney-airport.net/syd-arrivals-terminal-1