My question is how much space do they really save or is that not the point? I really don't know the answer and am wondering
As you suggest, it's not really the point of the stands for space savings (for me, at least). I like the option of displaying the planes on a desktop, and at various dive and climb angles.
I make a wall stand for my Pappy's Corsair. The plane sits on a well rounded off triangular-shaped piece of plywood (painted black). The plywood is mounted on 'lazy susan' style turntable hardware, which itself is mounted on a bracket attached to the wall. I like the display because it's something a little different, and you can rotate the plane 360 degrees to view it from all angles.
Laughinggravy2 confirmed my 'fear' about the stands in that the planes are not secured. That would not stop me from buying them, but I'd definitly make sure the the planes were secure (living in earthquake country always has one thinking about how things can get damaged by a shaker. BTW, my Corsair is secured to the plywood with fishing line around each wheel

).