" and you are dismissing that because you want humans to be the only things capable of originality."

I have not seen convincing cases of LLM's being capable of orginality. But they do have a lot of originality in their training data.

But then, human artists have a lot of training and influences too, so it's not so easy for humans to be truly original either (if that is a thing).

And then, if you are too original, no one will like it either ..

I don't think there is something "truly original" but in this concrete case, I suspect something very similar was in the training data.