The author never mentions artistic merit, presumably because it's a result of his premise. If you can't cheat at art, it's because there's nothing to cheat for, so there's no such thing as artistic merit.
I don't quite agree with your conclusion as written, because I think you can make the point that purely skill-based efforts do not have artistic merit. For instance, the frozen fish packager in an assembly may not be seen as having artistic merit in the his or her endeavors. This is because the effort is not creative, but following a process. It is not meant to provide any aesthetic value or entertainment, but is meant to achieve another objective.
On the other hand, if you mean that nothing intended as art can lack artistic merit, making the concept of "artistic merit" useless in that context, then I fully agree.
