It has been around for a few months now, and saw on last few flights.
At this time, some items are exclusive to pre-selecting. One example is on long-haul, there might be 2 choices of burgers, beef and turkey, available for pre-selecting, but only one available on board for pax who didn't pre-select.
On some inbound flights meals have been loaded at exact numbers +/- small margin, so it to be used accordingly.