Though you do have a completely valid point, it's also true that a lot of people should take some lessons from their example.
Until people realize that working a lot of overtime tends to generate a lot of technical debt, they'll keep doing it. And even though a 4-day week might be a bit short, you have to admit that it's working.
Working for them, a 4 day work week won't pay my two mortgages and won't put food on the table for my two daughters. Some day I hope to be there too, but it's advice I can't take now.
They have income coming in every month that is residual. As long as they have that income that isn't based upon how much they work then it works well. I believe the point is to get yourself into that position.
Until people realize that working a lot of overtime tends to generate a lot of technical debt, they'll keep doing it. And even though a 4-day week might be a bit short, you have to admit that it's working.