That's a very old fashioned perspective. I don't know where you work but modern workplaces, esp start ups, don't operate like that anymore.
Sorry, but startups typically still expect plenty of work, an extra full day off per week is going to be a fad for a minority of them in the same way that PR gimmicks like "unlimited time off" actually tend to mean employees taking a bit less holiday.
There is greater stock put in preventing burnout, esp for high performers which are the target of start ups and agile companies. It's not about hours and bums on seats anymore.
No there's lots of lip service about it and very little action in reality. And the basic fact of competition remains that overall people who choose to work longer can still get more done.
I remember a while back some games company made a big public faff about crunch time and how they were eliminating it... then surprise surprise went back on the whole thing when they were up against a deadline.
Google used to have something called 20% time where their brilliant engineers could spend a whole day per week working on anything they wanted, in reality, these days with people trying to push for promotion and do more, perform better than their peers how well is that 20% time thing going in reality? Are people actually spending a whole day per week on some hobby project? Or are they mostly trying to keep on top of their day job and make the best case they can for their promo pack and promotion to the next employee level?
People might be less productive on average in the additional hours worked but they still get stuff done and there are often competing pressures, new deadlines that get in the way of feel-good initiatives.
With unlimited time off employees who want to compete still won't take it, other also feel pressured (especially if not top performers). With notionally 1 day off per week, combined with remote or hybrid working then realistically similar things can easily happen, is the guy who is already behind on some deadlines still going to choose one non-weekend day that week to not work? Is the developer with multiple backlog items and a performance appraisal requirement to reduce the backlog going to take all their days off?
And on the flip side, is the guy who wants to do more, complete more and try and work on the new initiative he's proposed in order to earn a promo going to take all those extra days off?
There are inherently obvious conflicts of interest with all that stuff... I mean you could force 4 days a week and force no remote work and exactly 9-5 4 days a week only from the office and everyone out but in reality, hardly anyone would do that and in reality, most people work more than just 9-5 in any number of office jobs (plenty of jobs will have 9-5 but a culture of staying till 6pm or so) but especially in startups even more hours can be required and especially when close to deadlines. That's true of many competitive fields - big law, investment banking etc.
"yeah we've got a big demo on Monday for the investors and you've got your weekly extra day off on Friday/tomorrow, please do still take it off even though the demo isn't complete and we'll look like chumps if you do" as if...