I don't know why you got downvoted, but I find myself wanting to say some version of what you just said over and over again. People write extremely lazy, straightforward prompts and expect the LLM's intelligence to take care of all of it. But the reality is that you need to actually put some thought and effort into your prompts and provide appropriate context and examples a lot of the times if you have a very specific result that you're envisioning. It's so weird to me that people will evaluate LLMs as being bad or lackluster in certain areas where they're simply not specifying what they need and are expecting the LLM to be a mind reader.

I'm not saying that the GP is necessarily doing this. But having repeatedly had plenty of success myself in getting LLMs to write things the way that I want, with a little bit of prompting, it seems likely

There's centralized tooling for the PR descriptions, but I have some local flows where I try to provide more careful prompting and examples to get it to write better. It definitely helps but it's still not great and I'm often unsure if all the extra prompting is worth the effort.