Read a CX flight attendant FB post two months back. She mention that CX will usually cater 95% of the meals.

for example , long haul flight usually have 3 option
rice
noodle/potato
vegetarian noodle/rice.
usually they will prepare in 40/40/15% basis as some will order special meals.

But the issue is that they won’t know how many paxes will want to eat rice or noodle on that flight.

so for full flight, some paxes are only left with vegetarian.

so usually it is run out of choices. Not run out of meal.