> currently LLMs do not participate in natural language development
It's quite literally what LLMs are trained on. You create the core architecture, and then throw terabytes of human-generated text at it until a model that works with said text results. Doesn't matter if it participates in language development or not, it only matters that humans can communicate with it "naturally".
> Invented languages and codes
All languages are invented; the only difference is how conscious and deliberate the process was, which is a function of intended purpose. Just look at Esperanto. Or Valyrian.