Yes, you hit on the main problem with LLMs for writing. It doesn't cost you anything. It can do the reasoning for you and creating long messaging with dodgy reasoning.

I think you should write down your thoughts, tell it to make the points you spelled out and be concise and respectful of the reader's time and attention. When I do this, it works very well. But I agree if you just have it respond and reason it tends to often produces bad responses.