I think that the point, which the article may miss, is that we don't inherently understand them. We have to be taught to understand them—but we only have to be taught once to use a given set of icons, so it's good to use the same ones other people use, even if they're meaningless.
(I'd draw an analogy to "Why do we inherently understand menu items written in English?" We don't inherently understand them (witness non-English speakers); we just get to draw on our existing familiarity with English to make the understanding easier.)
(I'd draw an analogy to "Why do we inherently understand menu items written in English?" We don't inherently understand them (witness non-English speakers); we just get to draw on our existing familiarity with English to make the understanding easier.)