", but working 4 hours a day 3-5 (max) days a week will actually achieve peak results in my experience."

Yes, we max out on focus time ...

... but no, you're not a concert violinist. The rest of you time is all the other stuff - meetings, light reading, sales reps, catching up with professional colleagues, filling out forms, HR stuff, all the inquires from he newbies, returning emails, etc. etc..

The 3hrs focus/day is one kind of work, all that non-focus time is the 'work part of work'.

Literally most jobs is like that, it's 100% that kind of thing, there is no 'peak performance' it's just putting one foot in front of the next.