It's hard to describe. I think there's more nuance here. When you ask "What colour was the apple?" then I can "fill in" the colour and imagine a "red" one. But it's more like the details are filled in "on demand" or "lazilly" rather than "ahead of time". And like I said, it's not the same thing as actual visual hallucination.

It is helpful to have someone engage, for sure. I have a question for you: if you look at a 3d object that you can only see one side of, can you make inferences about the other side of the object? Can you rotate it in your head? Could you quickly be able to tell whether an object will fit in a particular hole, without actually trying it?