"leaders also need to create a culture in which employees do not have every waking moment of every day committed to project work"
Unfortunately, I am currently in situation where is lot more project work than people (and I wonder, is it different elsewhere?). In that case, I don't think the approach the author describes quite works unless you have a dedicated person who keeps track what needs to be done and prioritizes (i.e. project manager).
Because when I work on something I want to work on it with highest possible focus, not being bothered to asses what other work has to be done. So I would prefer (which is not my current predicament, sadly) some other person tracking everything and telling me - hey, this thing has higher priority than what you're doing right now, perhaps you should switch tasks. The point is, he should make the calculation that I should switch, not me.
(Perhaps this is a reason why preemptive multitasking won over cooperative multitasking on the OS level?)