LLMs will still blithely ignore the specs and steering documents, apologize profusely for doing so after the fact, and tell you "I'll do better next time" which they might do once or twice. But after the context is cleared or a new session opened, the Dixie Flatline gets reset and it doesn't remember it screwed up, or that you told it not to.

This happened to a coworker of mine. Generally the response from one-shotted devs is a shrug of the shoulders and "wellp, them's the breaks! As long as it looks sensible from 10,000 feet up it's still a huge productivity win." But the devil, as they say, is in the details.