> What if no-one had a mind's eye and Aphantasia is simply the lack of a delusion of a mind's eye.

The article proposes and falsifies a different hypothesis (that aphantasic subjects actually have a mind's eye but have the delusion that they don't) but the scientific argument is equally valid against this hypothesis. There is a difference in implicit behavior (in this case, priming during binocular rivalry), so the difference between aphantasic and non-aphantasic individuals seems to go deeper than metacognition.