That restaurant thing is a fan creation, it’s not official for PMDU and I was just reblogging it because I thought it was cute and cool.
Eating other pokemon is considered undesirable in Andalusst at least, and since there are no non-sentients it is morally questionable, but beyond civilised areas, tribal or barbarian pokemon often need to eat each other for survival.
Thankfully that’s avoidable in Andalusst where the problem can be circumvented by working together with other Pokemon. Most species can survive on berries, eggs, and certain meat substitutes that exist within the dungeons.
For example, giant mushroom steaks from the dungeons taste very similar to meat and provide similar nutritional benefits.