The output of an LLM is a reflection of the input and instructions. If you have silly and verbose comments, then consider improving your prompt.
Your assertion, then, is that even a 1 sentence prompt is as good as a 5 section markdown spec with detailed coding style guidance and feature, by feature specification. This is simply not true; the detailed spec and guidance will always outperform the 1 sentence prompt.
The plan mode is useful because if you do corrections during development mode it does that silly thing where it leaves comments referring to your corrections.
Fixed that for you.
The input is sooo much more than your prompt, that's kind of the point.