It's interesting because it's very obvious, biologically, that the panda has a digestive system that has a carnivore past, and yet, the very plentiful biomass in bamboo forests just waiting to be eaten rewards the animals that can make use of it. So the giant panda may or may not be "optimized" for meat, but has generations that came out of the free food that is bamboo, so that their very survival depends on a herbivore diet.