I remember another article from a Harvard business review where they studied the number of hours worked which was correlated with the highest promotion rate in business. 45.
So, if you’re riveting airplanes, or other manual work, 35 hours per week seem to be maximal. For office work, 45 hours per week at least gets you the best results from the business noticing your effort. I shoot for 45 hours a week on average, but sometimes go as high as 80, when sprinting, and as low as 25, when trying to recover from those sprints. Seems to have worked well for my career and work/life balance.
How long people actually work is not the same as how long they ought to.
And that's the source of controversy, with supervisors almost universally coming done on the side of "ought to work a lot more", or at least do things that supervisors perceive to be working a lot more.