Notice any difference between how your brain "behaves" reading fiction and non-fiction/academic works - e.g. reading for enjoyment vs reading argumentative discourse. For fiction, do you also find yourself guessing at the content or wandering off?
Both cases have similar pattern in terms of wandering off for me, but they are not quite the same. Reading for joy means enjoying the products of your own imagination, but sometimes it shoots over the line, I guess. Reading for work is more tedious, because its not for fun, hence the guessing distraction, like "yeah, I get it, but what about this and that?" Having understood the problem, reading the solutions then seems kinda obvious.
There is a difference, but both follow the same pattern, so: yeah.
I think, when my mind wanders off while still reading that means I got "bored" with the text by already knowing what's going to happen and I switch to associative thoughts instead. That's a problem for people who think highly associative instead of sequential. They need to apply or follow sequential logic actively instead of just doing it automatically, and that occasionally bores the hell of them, or exhaust them, because often they just know how things are. Hence the wandering mind in this case is a different one compared to the cases in the article.