Yes, basically all of these missives and thought experiments implicitly exclude retail while studiously avoiding admitting that this is the case. Retail stores need to be open a sufficient number of hours at the right time(s) of day to capture their potential customers. Unless you're not able to handle your checkout line or your restocks for whatever reason, "efficiency" doesn't really enter into it. Not in the sense of employee time, anyway. Maybe the world's best 7-11 clerk could check out a thousand customers in an hour but just because he can that doesn't mean it makes sense to close the store at 4:00 PM or only keep it open three days out of the week.

Edit: And to add to this before anyone pops out of the woodwork to state the obvious, this does not preclude the store from having more employees who work shorter shifts. In fact, this is often already the case not for any altruistic reason (to put it mildly) but rather to prevent anyone from achieving full time status such that the company would then owe them benefits.