I think this is only "statistically" true in the sense that training is based on facts and not non-facts (except maybe with the ingestion of flat-earthers literature ;-). The existence of hallucinations in a bare transformer shows that the convex hull is not about information but about text, so the limit may more be "possible linear combinations of text", which allows for much extrapolation and counterfactuals. True creativity may be one reinforcement learning mid-training goal away that rewards novelty over correctness.