This principle is likely the reason imperial units stick: they're fantastic for fast fractional math. For the same reason, it's easier to work with 360 degrees in a circle than 2*pi radians.
I guess they were referring to how a third of a yard would be a foot or 12 inches and that most people have an intuitive understanding of such common lengths. Also, because of the factors involved, “simple” fractions (e.g. ½, 1/3, ¼, ...) often end up at integral lengths.
But intuitive understanding of certain lengths is certainly not limited to the Imperial system. I frequently use A4 paper for measuring if I don't have a ruler at hand. I know the span between the tip of my thumb and pinky is pretty much 21 cm and so on. 8.2 inches probably wouldn't be much handier either.
As opposed to multiples of ten, in the metric system? Huh?