The bottom graphic is "ideal?" That doesn't look ideal to me. Visually at least, it looks to near-maximize the frontal surface area presented to the wind by essentially elongating the inefficient cylinder-like shape from knee to to cleat. The low heel technique would seem to minimize frontal area, with the surface area of the top of the foot being more "hidden" in terms of frontal area.

I'm talking purely about aerodynamic efficiency, not the biomechanical efficiency argument presented by the link (which could be a whole other thread).

Edit: I agree the high heel hides the cleat/pedal well. But at what cost?