This type of service is also a good way for an airline to reduce catering costs. If they know you have booked a particular meal, they don't have to cater extras to account for onboard choice. On SQ, from anecdotal reports, if you don't like what you pre-ordered, they will often let you have a different choice. I bet QF will be much more strict about "You ordered this meal, you must have it."
It really is emphasising that one should not expect a full meal service - just the abbreviated "supper" service. Hope the lounge provides enough to make up for what is not provied on board. But I'm more used to UA and AC which do provide a full meal on westbound evening departures.
I have done that route a lot perhaps 40 times or there abouts and not once have I felt like I needed a full dinner service at either 11:30 pm west coast or 1:30am west coast time (which is even later if you have started your day on the East coast, checked out of your hotel ahead of your breakfast meeting and have been up for 21 odd hours).
As long as you can still get the snack menu for when you wake up and still have 6 hours of your flight to Melbourne left and you are starving then I think this will be OK.