3 Sphere curvature highlighted

Note that the analogy fails for the green bit

From here, it can be seen that the spindles are 3D objects that lines the rind of the 3 sphere, analogous to how the spindles lines the surface of the 2 sphere

In my perspective:It seems the moment you tried to highlight the spindles, the spheres become flattened and sew together and become progressively bent towards south as it approaches the boundary sphere/biggest sphere in the projection (the spherical 3quator)

However the green part is still beyond comprehension, other than the fact that I know it is bent, but cannot seemed to fit the view nicely with a bent spherical cloth

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When switching interpretation A, the thing become hollow and saw the surface become 'paper thin' and the 3D bits bent like pieces of paper and apparently lose their 3D-ness. When switching to another interpretation, the whole thing is puffed up and 3D but then the hollowness feel dissapears and the 3D bits doesn't looked bent

i.e. I still cannot see the two interpretations at the same time

Diagram of interpretation A:

By focusing on the blue circle and with the understanding that the vertical black line is actually something shown the the mini diagram (A semicircle), the whole spherical envelope and volume (in the projection) becomes a huge tubular spindle thing extending from the lower vertex through the north pole to the upper vertex and that the whole thing curve southwards with the smallest sphere in the projection almost 'flat' and the rest of the spheres forming a dome and bend towards the south. The projection now looks like a hemi3 sphere and hollowness is now visible (sort of...)

IMO I think it is easier to see the thing concave northwards rather than convex southwards (do to the 3D shading of the projection)

And this is what I see in intepretation A

The two spherical spindle halves, folding them together according to the arrows will form a hollow 3 sphere

(However I don't think this is correct cause if this is really the case, then it will be a case where nD stuff embedded in n-1 D space, but not projection)