What's more surprising (I would say, crazy) is that anyone expects more. Nobody works at their top level for more than 2-3 hours a day. Maaaaaybe 3-4 tops. Doesn't mean you can't be productive for many more hours, but you are not gonna be able to work effectively on tasks that are anywhere near the limit of your ability. You just can't and nobody does it....not athletes, not artists, not writers, not philosophers, not mathematicians, ..- not anyone doing hard creative work
Also, for anyone doing that kind of work, things like walking around and socializing is both vitally recuperative and indirectly productive in its own right
It also depends on prioritizing high quality work. Plenty of places would be happy to have you at below optimal efficiency for twice the time to make up for communication inefficiency.
I agree. I think you cheat this some - depending on the medium - by separating time spent creating with time spent editing. In myself, I've noticed that editing can reinvigorate the creative process, but if I'd been creative earlier, the burst of creativity spurred by editing is short-lived, and I'm often ready for a nap when I'm done.
Also, for anyone doing that kind of work, things like walking around and socializing is both vitally recuperative and indirectly productive in its own right