The article implies a tighter knot is a more secure knot. So, the article makes more sense if you consider they're mainly talking about binders, stoppers, and fishing knots.

In contrast, most loops, bends, and hitches don't need to be that tight for them to be completely secure. Great knots like the Bowline, Butterfly, Carrick, Zeppelin, Sheet Bend, and many others are not that relevant to the article.