Yes, but the person you're replying to is talking to an employer who wishes they could hire someone to work 80% time for 80% pay, but somehow isn't able to do that (Hint: It's because they don't really want to)
Not as much as they would like to. I'd love to exchange a day for 20% cut, but it's not an option. Nobody will agree to that. Same with my colleagues. We don't need that 20% money but nobody cares. Even now when we're working from home at least a few days a week. It's simply not an option.
But thanks to global changes, country by country, this mentality will slowly be changed and finally 4-day week won't be some strange option but a norm.
You sure can, and you can enjoy not having health insurance, vacation time, retirement contributions, or anything else that makes working less unbearable.