I did write a reply and then HN wasn't responding, so that's here:
https://butterflyeconomy.blogspot.com/2020/08/shorter-work-w...
https://butterflyeconomy.blogspot.com/2020/08/shorter-work-w...
Some people really, really like having a regular three-day weekend and will do just fine getting in their hours in four days. Others may well prefer a five day week with fewer hours per day.
If we could cut hours and give people choices as to how to allocate them, more people might get on board with the idea.