If there were a concrete phenomenon that's consistently observable, I absolutely agree with that reasoning. But I don't see that dynamic in discussions of aphantasia. We can't directly compare subjective experience, so any comparison is going to be filtered through the language of how we describe said experience, and so it's that much harder to conclude whether aphantasia is a natural category and the extent to which people have it.

Thus I share the parent's frustration about the sound-and-fury (imaginable or otherwise!) associated with this topic.

Even when people do try to have a productive discussion about it, half of it is nailing down a test to distinguish whether you're "really seeing" an image or just speaking metaphorically. That, or an article (like this one) casually assumes away this measurement problem and goes into a diatribe about how trippy aphantasia is.

(Before you start guessing, I don't think I have aphantasia, based on its descriptions. I can imagine pictures, or at least I think I can, though not necessarily the crystal clear images others seem to see. I do poorly on "draw this complex image from memory" challenges, although I think I'm still drawing from my mind's "eye" when I do it.)

Now, if we want to talk about observables believed to be associated with aphantasia, that would definitely be interesting. But most discussions are light on that too, or casually assume all kinds of things are implications of the condition.

Basically, I'm not convinced we have a rigorous enough way to talk about this question for it to be worthwhile, so I usually feel like discussions of it are mostly a waste.