The author is approaching this as a human problem. Plots are not made for machines, they are for people to read, and the author specifically wants as many people can read and parse plots easily as possible. As lamentable as math education might be, we have to work with what we have, and I do think it is a reasonable goal. I agree with the author that it should not be necessary to know what quartiles are in order to see how spread out a distribution is.