The issue with short haul flights is that food gets heated very early on, and although they might be able to keep it warm for a couple of hours they have guidelines as to how handle heated food (they can't reheat it for example).
AUH-DEL is a short haul flight, it's not like there's a lot of leeway. Once the food service is over you'd probably get a little over an hour before descent, so not sure how dine on demand could be offered to begin with nor how it's something expected. You could ask them to hold off your meal option until an hour from landing but that's about it.