Ok, I’ll add my personal experience here. When I imagine something, like an apple, my perception of the imagined object ranges from a rather blurry apple to a very detailed apple, but anyway I do peceive it very visually. It’s definitely not just understanding in my case. I perceive the color, the shape, movements if need be, everything. When I do this, the normal perception coming from my eyes kind of shuts down and I only concentrate on “seeing” the thing I imagine, but if I focus I can also imagine something being somewhere in a real lication I see with my eyes, so then it feels a bit like AR. I’ve read somewhere that the same centers in the brain are active when you imagine something and when you see it, so you could say it’s a kind of deliberate visual hallucination. I can also do this with music - I can play it in my head and enjoy hearing it.