I'm glad someone did this, but It doesn't surprise me that the models are not up to particularly advanced story writing yet. I could see them writing some rather dry high-concept sci-fi fairly soon, but there are some types of story with interpersonal relationships that I cannot imagine a non sentient writer being able to produce. I wouldn't rule it out an AI being capable in the future, but I think if it did, it would mean we would have to seriously consider that it's a sign of a solid understanding of emotions and theory of mind.

I found LLMs very good at reading human chat logs and doing psychological analysis of the participants, and of the interplay

hard to imagine how they do that without a good understanding of emotions/theory of mind

if they pattern match to psychology books, that is still functional understanding since they can operationalize them