It's not necessarily less work per person, it's less time per person. That matters in cases where coverage is needed ( medical personnel, police, fire department, secretaries, phone support, hospitality, etc.) but in others where only the output matters ( like software engineering, lawyers, marketing, even factories in some cases etc. ), there have been multiple studies around the subject and they all claim that fewer work hours increase productivity.
While I wholeheartedly agree with you, I think we should be careful with this discourse.
Rather than increases in productivity, increases in production should be emphasized. And yes, you cannot increase labor production without an increase in productivity, everything else equal.
Iirc, increase in production is about 40%. So working Monday to Thursday, you produce the same as someone, working 5 days produces Monday to next week's Tuesday morning.
You're right. It's time spent and not work performed. Original comment edited.
However, in many professions being available for a given number of hours is often a major part of the job, and that means there will be a direct requirement to hire more people in order to cover the reduced working hours.
