Earlier quoted context omitted.
I think the confusion here is that you're taking what he's saying in terms other than those of topology. In topology, you deal with manifolds. Manifolds have no thickness , but they do have area. In topology, there's no such thing as a 'filled' sphere: a sphere in topology has no edges and an inside surface and an outside surface, much like a football. There are two ways you can make a 'bottle': you can deform a sphe…
Much helpful, thanks!!
Topology is an interesting area of study.