My quick and dirty interpretation of the theoretical backbone of the evolution the watchers are trying to push:
The origins of cuisine were for survival: energy source, possible medicinal uses, cooking and preservation techniques so that it's safe to eat, could last, and sometimes even be more palatable. As a civilization becomes more stable and food secure, then we see experimentation and the development of a food culture and supporting vocabulary. Sharing of food and ideas encourages trade, sometimes war (over desired ingredients), and innovation. Food here is really just a proxy/catalyst/vehicle for the development and spread of culture.
Taking a step back from the story, food is being used here because it's relatable to most of us, it's easy to show visually, and because food manga probably sells decently well. I mean, that's why I'm reading this manga; the philosophical bits are just the special seasoning that makes this a bit unique. But let's see if the author can actually deliver on the execution and flavor...