The visualizations are not showing actual mountain shapes. Instead they are showing the envelope of surface area as a function of height. For example, for the D

The visualizations are not showing actual mountain shapes. Instead they are showing the envelope of surface area as a function of height. For example, for the Diamond shape mountains, the base of the mountain is very steep and so has almost no relative surface area. The graphic is correspondingly skinny at the bottom. I think communication would be enhanced here if the visualizations were supplemented with idealized cross-section illustrations of how a typical mountain of each type would look. That is what the pictures of the actual mountains are supposed to convey but they don't really. In this case, a "stick figure" drawing of each mountain type would do a much better job.