I don’t think pg is talking about the short-term, cognitive deficiencies of using AIs during execution of a specific task. I read it as the long-term decline in capabilities because you don’t regularly exercise certain things:

- being able to organize and compose your thoughts

- being able to synthesize disparate ideas into a cohesive whole

- tuning word choice, diction, and flow for a particular audience

- choosing the narrative frame in which you present your idea (this one is huge)

More concerning than long-term decline is that the next generation never develop these at all.