In some regards the economist's predictions were correct as many people really only work 15 hours or less a week right now. The rest is meetings, chit chat, calls, emails, looking busy. But don't go home early or you'll look like you aren't dedicated.
It is kind of messed up situation and probably will eventually resolve towards efficiency.
Communication is necessary if you work in large groups towards common goals (row in the same direction).
That is currently done by emails, meetings and calls and are a necessary cost of business (obviously to a certain extent).
My managers currently target 25 hours of individual work with the rest being taken up by the aforementioned topics which I find a reasonable/maybe a little high balance.
15 hours of individual work per week is pretty low though.
A former boss once told me that he expected to realistically get about 3 hours of "real, productive" work from a person in a given day. The rest would be task switching, administration, and other overhead (including water cooler type socializing).
So that's about 15 hours a week, in a 5-day workweek. Problem is that a lot of that that overhead sort of has to happen to make the three hours possible.
Bucky Fuller calculated that we would be able to "make the World work / for 100% of Humanity / In the shortest possible time / Through spontaneous cooperation / Without ecological offense / Or the disadvantage of anyone." by some time in the 1970's...
It is kind of messed up situation and probably will eventually resolve towards efficiency.