I absolutely think that the 40 hours a week were chosen because of political reasons. That doesn't mean we should work for 7 days a week, or that the fact that we work 40 hours a week is a problem in any way.
The only thing I don't understand and have trouble with is people claiming that 4 days work week somehow results in them doing more work than they do in 5 days. To me it sounds like people have decided that they want to work less (totally reasonable) and then try to use "trust the science" method to make it happen.
Counterpoint: what makes 40 hours a week the sweet spot? Why is 40 more productive than 50?