That doesn't mean every employee and contractor is coming in to work 24/7.

A workweek is per-person, not per-company.

Yes, they operate 24/7. If the work week is shortened, companies wont operate less hours, they'd just spend more money on staffing. They'd either need to hire more people to cover 24/7 operations, or pay existing staff overtime to work their current schedules. Companies don't want to spend more money on staffing which is why they don't want reduced work hours even though studies show it's beneficial for people's lives.

I'm a bit confused by your comment. By workday, do you mean individual for employees, or do you mean "business days", like when banking and financial transactions are historically run?

4 day work week would be for individual (full time, salaried) employees, to have a 4 day/32 hour workweek instead of a 5 day/40 hour workweek (at the same compensation). Companies like Amazon running 7 days a week just means the business doesn't close down over weekends or such, but doesn't generally mean a given employee is working 7 days straight. (Though, it absolutely can result in employees working 7 days straight, depending on pay period, how weeks are broken down for scheduling and payroll, and whether overtime is allowed and/or encouraged.)

Yes, but so do hospitals?

That down mean that every worker has to come in 7 days a week tho, right?

And 24 hours per day. That's why they're using shift rosters.