A single month trial says nothing. A rational employee would surely work a lot during this trial period, because if the experiment is successful, they get a lot

A single month trial says nothing. A rational employee would surely work a lot during this trial period, because if the experiment is successful, they get a lot more free time in the future. Nobody works at 100% productivity all the time, but if it only about a month with a big incentive, they can tap into their reserves and improve productivity for the prospect of more free time. Social experiments are very difficult because the observed subjects know about the experiment.