Yeah, I was trying to make sense of the graph in the article, because even if I were carrying only 3 STEM classes per semester (sometimes it was more), then class plus at least 1 lab would come out to 10 hours per week, but these classes typically had problem sets we spent 4-5 hours on each week, so that's almost 25 hours per week before we count the other 2 classes I didn't mention, or study for exams. And if it was programming, most would have similar workloads, but some were notorious, so a single graphics or operating systems class might demand 15-20 hours of programming outside of class time the entire semester!

I think you're correct that experience will differ substantially by context. I think your particular generalizations might hold enough to show up in a regression but there's enough other stuff going on (and noise) that they won't be tremendously predictive in individual cases.

I was a STEM major, did well at a reasonable school, and the only time I felt like I had way the hell more homework than I could get through was at a community college when I signed up for a Literature course and a Political Science course the same summer.