Not trying to argue or anything, but from an etymological stand point, wouldnt "pescatarian" infer that you eat a diet solely composed of fish? Sort of how a "vegetarian" implies a diet of only veggies? (because "pesca" likely being derived from the latin word for fish, piscis) Which should make it sort of like a diet of a piscavore (carnivore who eats only fish).
I mean, in pop culture, it likely does mean someone who eats vegetarian + fish, but just from the word structure, if someone came up to me and said they were a pescatarian, i would assume they ate only fish. Honestly, up until now, i've never heard that word before.