I would disagree that it's a sweet spot for execs.

Essentially no one should be working 60 hours a week, the human mind needs breaks to unconsciously work on problems.

I would posit unless someone is doing pure labor, anything involving creativity / problem solving actually has worse returns past 30 hrs a week of intense work.

Anyone in exec positions claiming otherwise likely would hesitate to let someone actually see what they do all day / week. No doubt they "work" all day in some cases, but that day is filled with lots of non work / downtime.