There is a faq entry about that on tfa. The main differences are use of rsbuild (not a big diff down the line I expect, since vite uses rolldown now), and design to accommodate llm agentic development.

I did read that LLM generated paragraph but I was thinking there was some architectural difference/some improvement to existing tooling.

I don't mean to sound too dismissive but just slapping on rsbuild and well formatted errors + llms.txt doesn't seem that useful?