It may just mean that nothing is stopping a person marking their account as a bot (maybe in jest) and posting with it manually.

Alternatively it may just be semantics. Are fictional characters "people"? Does "person" imply sentience, or can it still be used in the archaic Roman sense of the word -- a persona; literally: a mask worn by a stage actor. In which case, if the bot is designed to imitate personality, it may be more apt to refer to it as automated than as a non-person.