We only really know what goes on inside our own heads. And unlike other things, like long covid, there's no outward expression of not being able to visualize.

And even for those who claim to be able to visualize, they'll admit that they aren't "seeing" the object. But it's difficult to explain what I mean when I say "I can see it in my head". But it's not. So it's hard to say whether what we're doing is the same or not.

Like the old bit about whether or not the blue you see is the blue I see. In the end, it kind of doesn't matter. If something is "blue", we both agree that the thing is blue, it occupies a certain wavelength, etc. So even though we agree that the thing is blue, we cannot know if we actually see it the same. But since the results are the same, the particular qualia doesn't matter.

We can't make that comparison with inner monologue or visualization. Which is why I guess it fascinates people.