I used fable, and directly compared it against sonnet 4.8 and gpt 5.5 on various tasks. It was generally better, but still not perfect. Going back to sonnet/gpt has been perfectly fine.
Depends on what is meant by "fully responsible" I guess. At my company non-engineers push code to production where the only reviewer is frequently an LLM, if the code is broken they get an LLM to fix it. The human does not understand the code, they are not even trying to, this is pure vibe coding. We also have engineers who push code to production that they have not written, and not fully read, and has not been read by another human (at least not in detail).
I would say that counts as "not having that policy". Based on what management tells us, we are dead if we don't operate this way.