IMO I'd call "AI Artists" a type of Art Director, since they themselves don't make the art but instead direct and dictate what exactly they want, and if the result is different they tweak their wording to direct the art into a different direction
Art Directing, whether for a human or a machine or otherwise, is still a skill itself and still has to be learned to get good results, but it's distinctly different from making the art yourself so I wouldn't call them "Artists" outright