Right, so the generalization “if you have to explain your UI then you failed as a designer” doesn’t apply to all UIs.
Is this critique to do with the div containing the text "Scroll down to read and explore"? It doesn't seem like a good critique.
It does apply. Assuming a baseline(e. g. "literate English" or "colorblind primate"), a UX designer should be able to create an interface that allows for the engineered function to operate should the operating entity desire that action by a mixture of prior shared knowledge and novel information. If the designer is unable to fully convey the functionality, then to some degree, the designer did fail.