Earlier quoted context omitted.
But I'm not sure what point you're making. If market forces can operate in a world with a 40 hour default work week, they can operate in a world with a 20 hour work week. At the macroeconomic level, we're talking about tweaking a coefficient. So what? By shortening the work week, we can give many more people an opportunity to engage in dignified work, give them more leisure time, and spur further investment in labor-…
That strikes me as a tangent, it raises many questions (What happens if I want to work more than 20 hours a week?). The idea of a "work week" is based on the salary model which is based on the idea that companies are magical job fairies that exist to provide jobs. What if I create a product and work on it more than 20 hours? What if I want to sell peanut butter at the local food market on the weekends?
I have friends in France who sneak into their academic research labs after hours because of this exact reason (well, not 20 hours, but set max work hours)... seems super silly to me.