I think what they mean is the "pixelation" (yes I just made that word up). The more jaggedy the lines look, the greater the angle.
Something I noticed while doing angle problems is that the more time I spend looking at them, the more I get wrong. You want to look at them quickly, go with your gut instinct and move on. Save the time for keyholes and pattern folding, I find them to be trickier.