Less isn't automatically more. A meal with four ingredients beats one with fourteen only if the four are right; otherwise it is a smaller meal.
What the principle is actually about is subtraction as a method. Musicians talk about the rests — a song with space in it hits harder than the same song with every gap filled, because the ear needs somewhere to put what it just heard.
Applied to a week rather than a shelf, it means three things properly attended to instead of eleven half-touched.
The difference isn't discipline. It is that the three get room on either side of them.