I seem to recall this principle was established scientifically and medically in the mainstream some several decades ago. There was an entire porcelain facility developed to replace an existing toilet, which involved supporting the entire squatting position with a "fitted" shape to support the back of thighs and the calves. It did not look like a typical toilet at all. It was written up in national publications, although I don't recall exactly which, but something rings true that in Parade Magazine (back in its heyday) may have been one place.
This footstool incarnation of the principle is certainly much less expensive and is easily adaptable to existing facilities.