I'm not aware of any empirical or historical justification for the range 28-56. People are indeed seldom happy unemployed, but I haven't seen any evidence that people would be unhappy on e.g. 14 hours/week (of course it's very hard to control for status aspects).

The kind of person who can cash in for millions is an outlier in many ways - the working habits of such people say very little about those of the general population.