1. Flights from Au can rarely connect to domestic destinations same day. Arriving on QF19 or the PR flights required overnight hotel anyway. So, a 1am (3am AEST) arrival. For me I'd be wanting to grab a hotel and take a ~10am flight.
2. We don't know what BI will throw at it. They usually seem to be consistent having arrived into MNL at various times from BNE, SYD, HKG & SIN.
3. 2-3am would be so quiet on the roads. But 5-6 will still make it. 7-9 not so much fun.
I have a sense that QF has made the timing decision based on aircraft availability/utilisation rather than passenger convenience. That's why I'm interested to see the pricing and if that pricing will factor in the inconvenience. A few years ago Jetstar had SIN-CRK flights at like Arr 3am Dept 4:30am and I never took that flight.