I could "write" this code the same way, it's easy
Just copy and paste from an open source relational db repo
Easy. And more accurate!
The actual task is usually to mix something that looks like a dozen of different open source repos combined but to take just the necessary parts for task at hand and add glue / custom code for the exact thing being built. While I could do it, LLM is much faster at it, and most importantly I would not enjoy the task.
It is a Rust reimplementation of SQLite. Not exactly just "copy and paste"