> I used an LLM to write assembler in my made up API so I don’t think what you say is true.

I think you are underestimating the amount of data/context that is required to use a battle tested general purpose language, for both humans and LLMs. The ecosystem requires official docs, stack overflow answers, blog posts, tutorials, existing source code, subreddits, issue/PR discussions of undocumented features, obscure mailing list threads with rare insights, books, youtube videos, benchmarks, tests suits... and the ecosystem of libraries for the language that also need their own official docs, stack overflow answers...

You also need the collective audit by the community and assurance that this language has been used in production by countless others.