I've googled around a bit about fixing foot problems ("fixing flat feet", "reshaping the feet", "fixing fallen arches", etc.), but the whole concept of "kidney bean shaping" doesn't appear anywhere else.
And it's not the just the phrase that I'm not seeing, but the entire concept. When I watch videos of people with good arches talk about fixing one's arches, even if they have a nice kidney bean shape, they don't talk about it. Nobody else talks about actively changing the horizontal layout of the foot before beginning an exercise.
The same problem occurs when I read about "foot shape". Based on the internet, the only aspects of foot shape are length and arch height. Here's an example:
I'm not saying they're right, I'm just concerned because this complicates things. When I mention "kidney bean" shape at a shoe store, no one knows what the heck I'm talking about. Is there a special codeword I have to use for this concept?