I think something like an x86 -> ARM change is perfect example of something where LLM assisted coding shines. lots of busywork (i.e. smaller tasks that don't require lots of context of the other existing tasks), nothing totally novel to do (they don't have to write another borg or spanner), easy to verify, and 'translation'. LLMs are quite good at human language translation, why should they be bad at translating from one inline assembly language to another?

Yeah. Lots of busywork where if you had to assign it to a human you would need to find someone with deep technical expertise plus inordinate, unflagging attention to detail. You couldn’t pass it off to a batch of summer interns. It would have needed to be done by an engineer with some real experience. And there is no way in the world you could hire enough to do it, for almost any money.