Are there actually any humans who can reason about things like cache performance from first principles? I know there are some people who think they can, and I suspect they're fooling themselves. The one iron principle of micro-optimization at the level of cache hits is "measure, measure, measure", you just cannot think your way to the right answer on the first try. Processors and instruction sets today are too complicated, and tips that worked on one generation might be neutral or worse on the very next revision, making all the cargo cult knowledge passed around on this topic at best useless. I'll echo one of the sibling commenters here and say that LLMs probably bullshit their way to answers on questions like this because that's what humans online do as well.

If you give an LLM a proper testing harness and feedback loop to actually generate hypotheses, test them and revise them, I suspect it will do much better.