I think for a fair number of HN jobs people are being paid for success in a certain sense: someone needs to know how stuff works and keep an eye on the systems,

I think for a fair number of HN jobs people are being paid for success in a certain sense: someone needs to know how stuff works and keep an eye on the systems, but the level of effort varies greatly. When something breaks people can end up working really late, but when things are smooth it's not stressful at all and you can read HN. While the business is making money, it's happy to share that with the devs, even if they can see that people aren't busy. There are also jobs where the output is open ended: you can work more on those powerpoint slides, or you can declare victory early and it will still look like a slide deck that's finished. In that sense there's not really an "amount of days worked" and with WFH this gets even more blurred as you don't even need to go anywhere. There is a sense in which this is detrimental for such workers to go to 4 days. Employers will pressure people to get paid 20% less, for effectively the same work. This is especially the case with women who feel a lot of pressure to be with their kids. The employer takes the other side of the above deal and feels entitled to the same work (which is nebulous). This has effects on both pay and career advancement, and stress. My wife got offered one of these "deals" and rejected it, mainly because her boss seemed like an exploiter.