Even the subconscious can't register facial expressions that the eyes don't actually see, as is the case when Snape is reading his exam questions while the Marauders interact nearby, or when Snape is making his exam and Harry goes to look at the Marauders. Nor can the subconscious explain why someone using the Pensieve can actually see the person whose memories he's in - if it was really strictly limited to what that person actually remembered, surely the Pensieve user would be looking through his or her eyes.