If we are talking about SYD curfews and WSI, then the actual big question is would WSI be the alternative airport to land if incoming flights missed the curfew dateline.
Common sense will say “of course “ it save fuel etc, but this doesn’t make it any easier to reposition airplane or staff (if Sydney is their home address, unless they live in the west).
And worse is WSI would need to coordinate with SYD much more closely for airplane reposition (due to short distance and flight time) and it would not be happening first thing in the morning when shoulder period of curfew is reserved mostly for incoming international flights.
If those who missed SYD curfew and land at WSI, you can bet there isn’t a line of bus there to transport them to SYD that night,( if at all)
Hence we are talking about public transport to 24 hr WSI, for those people who landed in Sydney and yet still far from where they want to be.
As for those who knew they are on a flight with scheduled arrivals after 11pm and 5.30 am, and didn’t make contingent plans to get to their destination then, that’s another matter