I would say that it means "an automaton that isn't really an automaton". :) It was a good catch to notice the other interpretation. I think it's probably not that, because using the copula "to be" to indicate that something exists (an existential clause) is relatively rare and archaic. Descartes' "I think therefore I am", meaning "I think therefore I exist", is an example of that, of course. But if Descartes were philosophizing today I think he'd almost certainly use the latter expression.