I don't think it has anything to do with the number of seats. Any airline will try to minimize the wastage. Lufthansa now serves business class meals (with some differences) in first class for departures from the USA, probably to minimize costs and to reduce wastage. That way, with a larger pool of pax, everyone in first class will get their first choice. I think airlines have become good at predicting how many particular meals should be loaded, and while it sucks to be on the receiving end when mishaps occur, such as with the OP, I think they are an exception rather than something that happens all the time.