I don't think that the author is saying to "un-design" at all. She's saying to use a basic framework as a starting point and learn how to make it your own. Adding the fonts/colors/images that you feel add to the site are your own creativity and a way to break away from the typical Bootstrap site that is commonly used today.

Obviously it isn't advice a designer would take, I feel its meant more from one programmer to another and gives a way to make your demo less stereotypical.