But that's kind of my point - when I was originally working on it - I didn't know there's a more idiomatic approach - why would I copy paste the docs to ask it to improve the results ? Especially given the LLMs tendency to hallucinate and gnerate noise when asked to "improve code".

Also without reading the docs would I be able to spot why the idiomatic approach is better from single use case ?

You're basically depending on LLM to make choices for you - and in my experience so far it makes very suboptimal ones.