> The top tier LLMs would be as good at this as a lot of maintainers, right?

In some respects maybe in others less so.

So in my situation I am using a client for a system and am using a very specific part of it even though there is a lot of other complicated code in other parts of the client. A LLM is good enough to maintain the code path I am using and of course any changes are triggered / watched over by me. In this situation I am comfortable letting LLMs do most of the code. I would be less enthused if that was outside of my control and the code changes were more often and faster.