It's not a mental disorder. The brain is a very complex machine. It would be quite surprising if every brain would work exactly the same.
It's possible what people have talked about here is a pretty normal spectrum between the extremes of hyperphantasia and aphantasia. Especially aphantasia is not well researched yet.
Not being "neurotypical" whatever the fuck that means, has become SUPER trendy. Out of nowhere, suddenly everyone has a mental disorder.
I don't fucking buy it.