Comment by robotsliketea

It seems that LLMs often insert new ideas even when asked only to polish writing without changing it: https://bsky.app/profile/tomerullman.bsky.social/post/3mq33c...

I don't think this is surprising. Good technical writing is very precise. If you're starting from non-technical writing, I suspect that in most cases you can't make it "sound scientific" without adding new claims or changing the meaning. (Maybe you are being more careful, but this is something that worries me in general.)