This is a rather alarmingly bad piece of logic from a prestigious source:

The Committee employed investigators to collect data from the munition plants and to conduct surveys of the health of the workers. From the data collected, the Committee made a number of recommendations including mandatory shorter working hours, the avoidance of continuous night shifts and, above all, giving workers at least one full day off from work each week.

This study revisits the data collected by the Committee’s investigators and determines whether the Committee’s recommendations are supported by this new examination. It finds the Committee’s recommendations fully justified. For example, with respect to the value of one day off work each week, Professor Pencavel calculates that the week’s output was slightly higher when these munition workers worked 48 hours over six days than 70 hours over seven days.

Excellent. So there's an optimal length to the work week then. All work and no play produces not just dullards but lower output.

So, what would we expect a profit making employer to do then? Correct, try to determine where that optimal work week length was and then employ people for that period of time. But what does our professor suggest instead?

‘Instead of viewing restrictions on working hours as harmful restraints on management, statutory regulations on hours may serve as an enlightened form of enhancing workplace efficiency and welfare.’

He's using the proof that a profit maximising employer doesn't need such regulation to argue for such regulation.

Most, most odd.