The difference is consistency. You can read a manual and know exactly how to oil and refill the tank on a chainsaw. You can inspect the blades to see if they are worn. You can listen to it and hear how it runs. If a part goes bad, you can easily replace it. If it's having troubles, it will be obvious - it will simply stop working - cutting wood more slowly or not at all.

The situation with an LLM is completely different. There's no way to tell that it has a wrong answer - aside from looking for the answer elsewhere which defeats its purpose. It'd be like using a chainsaw all day and not knowing how much wood you cut, or if it just stopped working in the middle of the day.

And even if you KNOW it has a wrong answer (in which case, why are you using it?), there's no clear way to 'fix' it. You can jiggle the prompt around, but that's not consistent or reliable. It may work for that prompt, but that won't help you with any subsequent ones.

The thing is, nothing you've said is untrue for any search engine or user-driven web site. Only a reckless moron would paste code they find on Stack Overflow or Github into their project without at least looking it over. Same with code written by LLMs. The difference is, just as the LLM can write unit tests to help you deal with uncertainty, it can also cross-check the output of other LLMs.

You have to be careful when working with powerful tools. These tools are powerful enough to wreck your career as quickly as a chain saw can send you to the ER, so... have fun and be careful.