Ask these people to actually draw or paint the apples, and it quickly shows that they do not do lighting and shading correctly. Even with a lot of training.

Just look at art history. Only very few people managed to render things somewhat accurately before the invention of photography. And the consensus is that these exceptions (such as Holbein or Vermeer) used technological tricks to aid them.

My hypothesis is that people have an internal imagery that is extremely realistic and detailed, because they perceive the actual world in exactly the same way, using the same processes. One does not "see" the image on the retina in their mind's eye, one "sees", if I'm allowed to use the metaphor, the vector embedding somewhat further down the line.

Now, if people train their mind to actually see more detail, they find out that the brain is actually rather limited in comparison to a camera.