The author says they could narrate their own thought process out loud.

I couldn’t do that. I have no insight into my thought processes whatsoever. There are no semantic (or any other) processes to witness. It’s complete crickets at all times…

My wife is the opposite - constant chatter in her head. And she can trace every thought exactly. (No idea how people like her can focus or even function!)

We focus/function via the inner monologue. It doesn't just do its own thing while we're trying to focus or get something done, it walks through the issue and comes up with solutions and then criticizes them and iterates, and as far as we're concerned, that's us solving the problem.

Anendophasia? Fair number of people have this.