That's one of the things. Even in human-written fiction, the depths of any character you read about is pure smoke and mirrors. People regularly perceive fictional characters as if they are real people (and it's fun to do so), but it would be impossible for an author to simulate a complete human being in their head.

It seems that LLMs operate a lot like I would in improv. In a scene, I might add, "This is the fifth time you've driven your car into a ditch this year." I don't know what the earlier four times were like. No one there had any idea I was even going to say that. I just say it as a method of increasing stakes and creating the illusion of history in order to serve a narrative purpose. I'll often include real facts to serve the verisimilitude of a scene, but I don't have time to do real fact checking. I need to keep the momentum going and will gladly make up facts as a suits the narrative and my character.