Yes, it's harder to evaluate whether someone can visualize well, but that does nothing to invalidate my point.

Have you actually dedicated significant time to trying to learn how to visualize? I suspect that if you did, you'd realize: oh, wow, maybe I can actually get better at this. If most people who give it a serious effort also come to that conclusion, I feel like we've pretty much settled the question. So it is testable, just not as easily.

> Have you actually dedicated significant time to trying to learn how to visualize?

I haven't had to. I don't have aphantasia. Visualizing doesn't feel like a learned skill to me. It feels like something I've always known how to do. Of course if I pay more attention to what I'm doing, I can visualize in more detail than if I just do it casually. But I've never had the feeling that, oh, if I practice this and learn I can get better at it, the way, for example, that I can get better at playing the piano by practicing.

Where I'm stuck is, if someone else who couldn't visualize asked me to teach them how, I wouldn't know what to do. Whereas, if they asked me to teach them how to play the piano, I'd at least have some idea.