At the margin means that both languages, or frameworks or whatever, are reasonably appropriate for the task at hand. If you are writing firmware for a robot, then the LLM will be less helpful, and a language such as Python or JS which the LLM is good at is useless.
But Thomas's point is that arguing that LLMs are not useful for all languages is not the same as saying that are not useful for any language.
If you believe that LLM competencies are not actually becoming drivers in what web frameworks people are using, for example, you need to open your eyes and recognize what is happening instead of what you think should be happening.
(I write this as someone who prefers SvelteJS over React - but LLM's React output is much better. This has become kind of an issue over the last few years.)
