This chart isn't proof of anything. Body fat percentage correlates with - but is not determined by - how muscular someone looks. How much of your lean body mass is muscle, how that muscle is distributed, what your insertions are like are all factors in how different people would look at an identical bf%. Some people are muscular enough and are built in such a way that they'll be visibly defined even at relatively high percentages. Some individuals may have low body fat percentages, but don't have enough muscle mass to look very defined despite that.