You still need the world made inside a sphere to get the initial start.
this is because objects need to initially bend up and over.
faking it with a material function that shifts verticis is another way to do that i suppose…
The effect you have is then probably generated by using an ortho render target projected onto a sphere, which causes the deformation explained.
Not sure if the whole thing would then just be looking into the sphere with the render target material, or if the objects blend in at some point so you are actually walking on the real surface…