Another possible angle (to be mixed and matched with the original):
French guy works 35 hours (ok really 38) and is busy all the time at work.
Korean guy works 60 hours (ok really 55) and spends much of it 1) recovering from semi-mandatory drinking with the boss and colleagues, 2) browsing / shopping online, 3) chatting on KakaoTalk, often while 4) waiting for his boss to leave so that he can also, or 5) if working diligently, often on polishing pointless powerpoint presentations.
You forget that the American is working 50-60 hours, and only being paid for 40.
"Adults employed full time in the U.S. report working an average of 47 hours per week, almost a full workday longer than what a standard five-day, 9-to-5 schedule entails. In fact, half of all full-time workers indicate they typically work more than 40 hours, and nearly four in 10 say they work at least 50 hours."
So they're more efficient, while Americans are more productive because they work longer hours with less holiday.
> There's a big difference here. Obviously there's diminishing returns after X hours of work in a day or week, but there are still returns.
But where those returns are going are most important for this discussion. And they are not going to workers.