Maybe that are two different thing? Some may experience what is in their head the same or very similar way to how they would experience it if they would actually see it, but I think that doesn't mean that what is in their head must be static or photo-realistic. I suspect these are important factors, too, in a reference image you use for drawing.
I mean - it's either similar or it's not. Things I see with my eyes are definetely photo-realistic. So mental visualisations similar to that would also be photo-realistic. If they're not - they can have interesting qualities, but they're not similar.
