I definitely agree that mind wandering is where a lot of creativity happens and that it shouldn't be dismissed as just extraneous activity.

However, I think in this case, the author is talking more about this kind of mental baggage that people accumulate while scrolling through Facebook feeds and the like. We're essentially - whether we like it or not - memorizing crazy amounts of unnecessary information, and thus throttling creativity because we're still processing where Kathy went on vacation and what she ate there.

I try to reduce FB feeds, and try to read more offline, as too many low-quality thoughts are not only eating time, but are tiring and distracting, with little benefit.

But... this is more like "tough rush", a very opposite state of mind to "mind wandering" (even if both are different from the "animal-like" focus on current stimuli).

I agree. My favorite scene from "No Country for Old Men" is when Sheriff Ed Tom Bell figures out how the killer executes his victim, in the middle of a restaurant conversation with the wife of the hero ("My mind wanders" scene). It struck me as the exact way in which I have often thought. I read the book to realize it was not there. Must be an original contribution of the Coen brothers.