You can use LLMs in multiple ways, from very hands on to make local changes to completely hands-off.

I've seen plenty of code that was LLM generated but the commit message itself did not have the co-author attached to it. This only seems to happen when someone's interface to the codebase is completely though Claude/Codex/..., and those are usually the most verbose commits, and yet they say the least, because they just summarize the code changes, not the why.

On the other hand I've seen developers using Claude as a tool. They have VSCode open and a terminal window with Claude and go back and forth, ensuring they write correct code, and leave the plumbing to Claude.

So maybe the author of the code started off small and it grew over time?