While certainly some of that does happen. The language around visualization is complicated. But we know that there are people who have no ability to think in language and have no internal monologue, whereas others can do so strongly. Given how much variability there is in everything else with the brain, it would be rather strange that it isn't also true of visualization.
After all, everything we experience is our brains' interpretation of our sensory inputs. And if we can visually experience things that don't exist, whether through dreams or hallucinations (drug induced or otherwise), it stands to reason that if your mind knows how to control those same pathways you could create images in your mind.
After all, everything we experience is our brains' interpretation of our sensory inputs. And if we can visually experience things that don't exist, whether through dreams or hallucinations (drug induced or otherwise), it stands to reason that if your mind knows how to control those same pathways you could create images in your mind.