It's so obvious to some and may never be considered by others.
If someone asks about AI I tell them step 1 is ask it how to do something you know all about. Step 2 is consider everything else you ask will be that inaccurate.
As a dev with three decades experience writing code, I use it for stuff I know all about all the time. And these days, the majority of the time it is more correct than I would've been without a few iterations of trial and error.
GP is saying that when you use it in a domain where you're familiar, you'll naturally spot bad or lazy approaches and heavily steer the LLM, so you should keep that in mind when using it in domains you aren't an expert in (and thus can't as easily spot those things). I'm not sure why the tone of your reply is so uncharitable.
If someone asks about AI I tell them step 1 is ask it how to do something you know all about. Step 2 is consider everything else you ask will be that inaccurate.