In my experience, crew split the larger cabins into sections. So in a 12 row A350 cabin, row 8 would get their order taken sooner than row 6. And the A380 J cabins appear to work on 4 row sections.

That said, I have also gone hungry in the past on flights where I sat at the back of a.4 row cabin that was completely empty 2 hours before take off, but full at final departure with op ups whose orders were taken first...

Even so, some crews still manage to take orders by FFP status first, and will magically "find" your first choice if not initially available when asked for