I'd encourage you to dig deeper, they have lots of videos on the website with lots of different people of various conditions using the product (including someone with 1 leg).

Plenty of people out there are on the edge of walker/wheelchair that could benefit. As you suggest, everyone's medical history and capacities are different. But not sure where the "need to test this on people who rely on wheelchairs and walkers and not people who don't need them" comes from. Pretty clear that's happened.