With all their statistics SQ would easily see the CGK-SIN-SYD load and would have concluded that they are sitting on a goldmile simply by flying CGK-SYD directly.

For many Indonesians flying SQ is like a status symbol and I can imagine that J will be heavily loaded.

I'm surprised they didn't put in a three class configuration for this flight as I would imagine there to be enough takers for First as well.