This is a bold statement. I don't think I can get more things done when I take one more day off. Can you? They don't show how they measured their productivity

This is a bold statement. I don't think I can get more things done when I take one more day off. Can you? They don't show how they measured their productivity exactly. I also don't think a month trial is good enough to derive the conclusion. Furthermore, there is a chance that other variables affected the result. It's difficult to come to the conclusion through this kind of uncontrollable experiment where you cannot control the variables and constants.