Thanks for posting this, although I think you may have gotten the terminology a bit wrong.
"Dine on Demand" typically denotes a concept where there is no set meal time on board, but passengers can choose to have their meal(s) at any time they like and crew will accommodate. It's something QR offers in Business and many airlines offer in F.
What TK seems to contemplate introducing is a meal pre-order service (SQ calls this"Book the Cook"), where pax can select their meal from a broader range of dishes prior to departure, and the flight will then be catered accordingly. But it doesn't mean that they can then have their meal whenever they want.