For those who need math....
Each shoe with a heel has an angle built into the top of the heel. This is the heel pitch. The purpose of heel pitch is to extend the leg visually. However, in most shoes with heels of more than 1:8 total pitch (think roof pitch), the heel pitch is greater than the total pitch, and this leads to the foot sliding toward the toe. This makes it impossible to put significant weight on the heel, or to transfer significant load to the heel contact surface. As a consequence, these shoes are often the ones that are uncomfortable to wear. Shoes with a heel pitch that is lower than the overall shoe pitch will not visually extend the leg as much, but will be more comfortable as the weight is distributed more evenly over the sole of the foot, and consequently over the sole of the shoe.
Looking at Little Bike's boot, if the interior sole profile is the same as the exterior, it is overpitched, and she could not possibly get weight down on the heel.
An image to assist: