We got brass bands with brass instruments, synth music from synths.
We know therefore, necessarily, that they can be nothing novel from an LLM -- it has no live access to novel developments in the broader environment. If synths were invented after its training, it could never produce synth music (and so on).
The claim here is trivially falsifiable, and so obviously so that credulous fans of this technology bake it in to their misunderstanding of novelty itself: have an LLM produce content on developments which had yet to take place at the time of its training. It obviously cannot do this.
Yet an artist which paints with a new kind of black pigment can, trivially so.