I got to observe a similar thing firsthand in Japan: People staying late into the night, sleeping at their desks, wearing themselves out, even to the point of karoshi ( https://en.wikipedia.org/wiki/Karoshi ).

But in terms of actual productivity, I observed lots of activity and little actual achievement. What buoyed their productivity was the technology of a freshly rebuilt economy and industry post-WW2, which, coupled with a few innovative ideas, gave Japanese industry a powerhouse advantage to the point that it almost didn't matter what the workers did. They could have worked 2 hours a day and still had the same output (not the factory line workers, of course).

When the economy went sour in the 90s, there was no change in work ethic; people still worked late into the night, and still had the same levels of activity with the same levels of achievement, but the technological industrial advantage had dissipated over the years and they were no longer competitive. Same input, less output.

Long hours work against you. We've studied this to death, and the results are clear.