I think the author is trying to point out that mean, median, and mode are things that people think they understand because they know how to calculate them - any

I think the author is trying to point out that mean, median, and mode are things that people think they understand because they know how to calculate them - any one of them is trivial for the majority of the high school educated population (14-18 years old). However, just because you can calculate something doesn't mean you know how to properly apply it. When you taught your intro stats class, did you try to give the students guidance (and convey understanding) as to when and why they should apply one of the statistics? If so, good on you, but from my, obviously anecdotal experience, that has not been the case.