Will work just as good as today or 20 years ago.

Are you suggesting AI coding was as good 20 years ago as it is today?

I think they're being sarcastic, saying that rewrites from scratch have rarely worked well (whether done by AI or humans).

Exactly. Sorry for not being explicit about it. I thought it was clear enough, because 'this code is crap, let's just rewrite the whole thing, doesn't look to hard' is kind of famous for being a bad idea most of the time since forever.

It sure wrote less crappy code.