You're conflating why people want to rewrite it in Rust vs what is the likely end result i.e. I do think people want to rewrite things in Rust because they believe long-term it will mean fewer (memory safety etc.) bugs especially because there's been almost no meaningful improvement in this space for a long time. But of course in the short term it will mean regressions compared to the established C written version.

That is different from AI where the calculus seems to be that if AI isn't involved, it aien't relevant.

That remains to be seen, but my guess would be that if you do it like Ladybird (with human-in-the-loop and a decent level of review) then probably yes, if you do it like Bun (1M LoC in a week) then probably no.

I did recently read an article about how, due to better training data, an AI writes better code in Rust than most other languages.

How that translates to the number of bugs, I don't know.

I would think that existing bugs would be caught, but new bugs would be introduced. The problem remains, but at least it has a new name now.