Ahhhhhh, I see what you mean now. It's a very difficult subject to broach certainly but not impossible I don't think. My sister is aphantasic so I have some history discussing it with her; if you are perhaps having doubts about the existence of people who can't visualize because you are under the impression that it is a misunderstanding caused by the limitations of language I don't think you are entirely correct. The language barrier is definitely an issue that causes significant confusion when the subject is discussed but my anecdotal experience with my sister atleast confirms the extreme values to me. When she was young and being taught how to count and do math she really really struggled; at one point my parents, her teachers others who attempted to help would try helping by telling her to imagine some apples then add/subtract a few or count the amount of apples, stuff along those lines and it never helped because she was completely incapable of visualizing. Often her response to this approach was essentially "wdym visualize?" and no amount of explaining would help. To this day the only way she is able to do math is entirely through memorization of formulas, she has no conceptual understanding only mechanical. I'd often talk to her about my books and when I'd describe a particular scene to her she'd question how I was able to come up with it all. How could I describe something I had not seen?

Again I don't think the numbered scale is efficient for anything other than playful conjecture nor do I even think it's possibly to place someone on an actual spectrum at any point other than the extreme values because all of it is subjective and vulnerable to personal interpretation. There is no objective way to study this except maybe possible through the actual electrochemistry of the brain but I don't know anything about that and I'm just guessing.

It's also entirely possible that you never thought any of that and I wrote this for no reason but in all honesty I think I often write comments like this to help myself understand my own thoughts. Writing them out tends to help work out all my internal contradictions.

Sorry about the wall of text lol