They aren't saying that dogs are incredibly inefficient – looks like dogs are right where they "should" be based on their body weight. The point of course stands that bikes need a flat ground to be efficient, but this isn't some sort of competition or measure of moral worth. It's just an observation that given that we've already filled human-inhabited spaces with nice flat surfaces, cycling happens to be a really efficient form of locomotion. Fish also need to be in water to be able to move at all, but that's immaterial for the purposes of the chart.