Do you have the actual menu.

Even on the much later departing SIN services (eg QF6 which departs at 2300) there are usually some more substantive options offered in the Snack section.

While myself (and I suspect most) would eat at the airport/ in the lounge (noting that 8.30pm at NRT is 9.30pm in SYD) and then sleep most of the flight,

QF certainly do need to provide for those who are operating in different time zones or say transiting to South America and may want to stay awake and eat.