I’ve been around long enough to realize that everyone works at different pace. Forcing people to do what they don’t like will only make them quit or do a poor job.
I agree this depends a lot on so many factors like the type of work, work environment, team cohesiveness, company culture and pace, the person calling the shots and so much more. I am also a proponent of a shorter work week. But I know that 2 of my days are not the same as 2 of someone else’s days as I’m usually ultra productive. Hard to say how to best balance highly productive and less productive people on the same team - my guess is take slow and reduce work hours gradually to see how people handle it.