I think that is more that a staff-plus engineer is going to be doing a lot more management than "actual work", and LLMs don't help much with management yet (until we get viable LLM managers shudder).

LLMs are like a pretty smart but overly confident junior engineer, which is what a senior engineer usually has to work with anyway.

An expert actually benefits more from LLMs because they know when they get an answer back that is wrong so they can edit the prompt to maybe get a better answer back. They also have a generally better idea of what to ask. A novice is likely to get back convincing but incorrect answers.