# contradiction in ripple calculation for buck converter

I am having problems understanding ripple calculation for buck converter here (from page 39).

First, the author makes an assumption that the capacitance is large enough so nearly all [not all] of the inductor current ripple flows through the capacitor, and very little flows through the load. This assumption is valid.

However, in the calculation in the next pages, the author is calculating as if ALL inductor ripple current flows through the capacitor, no current flows through the load. Then he calculates for ripple voltage.

However, if we use the assumption that ALL inductor ripple current flows through the capacitor, no current flows through the load then the output ripple voltage should be ZERO. It doesn't make sense to me. There is a contradiction here.