Humans make subtle errors all the time too though. AI results still need to be checked over for anything important, but it's on a vector toward being much more reliable than a human for any kind of repetitive task.

Currently, if you ask an LLM to do something small and self-contained like solve leetcode problems or implement specific algorithms, they will have a much lower rate of mistakes, in terms of implementing the actual code, than an experienced human engineer. The things it does badly are more about architecture, organization, style, and taste.