It would be an irresponsible waste of limited time and budget for a human to write this which is probably why it did not exist before.

I wrote the first version by hand in C, and then rust.

The LLM was able to rewrite it with no dependencies implementing the low level system calls and test suites that would be a nightmare to do by hand.

The best use of human time for something like this is code review.

If your input is LLM-generated code, it's like taking snippets from Stack Overflow. You understand it fully and then make it yours. As long as you're hand-crafting the result, you grasp how it works.

This is an aspect of LLMs that probably shouldn't be understated.

I'm working on a validation tool with a coworker right now. We are meat-proxying it into existence, using less than two exchanges per day of his LLM validator and my LLM authoring engine (we could consolidate, but he's got some context I don't have and it would take more than zero engineering effort to ship it to me when PR messages through GitHub are a good-enough channel).

If not for the LLM, the tool wouldn't exist at all because we can't justify dedicating much of any engineering time to building it. But LLMs drive the engineering cost very close to zero, enabling the authorship of code that would never find engineering cycles otherwise.