> What it's telling you is that a company would rather have 4 people working 5 days a week than 5 people working 4 days a week. The reason for that is, productivity drops a lot when it's spread out over multiple people.

Why make that assumption? The company has a lot of per-employee fixed costs, which means that it's much more expensive to have 5 employees than 4 employees under the assumption that total productivity is exactly equal in both cases. (And the further assumption that you pay more productive workers more than you pay less productive workers.)

If you want flexibility on the work week, get rid of the concept of "full-time employee" status and make everyone contractors.