Well here's the
basics for review and a conceptual
illustration so that we'll be able to explore the extreme cases ...
The size of the umbra and penumbra are dependent on the surface area of the light source and the surface area of the object. If our object has a bigger surface area and completely covers our light source then only the umbra exists outside of the object. Consequently, if the light source covers our object then only the antumbra exists between the object and the light source since the object is entirely visible within the light source ...
In the case where the surface area of our occluding object is getting infinitesimally smaller then the umbra and penumbra are getting smaller while the antumbra is getting larger. For the opposite case where the surface area of our light source is getting infinitesimally smaller relative to the object then the antumbra and the penumbra will get smaller while the umbra will get larger as time goes on ...
Points lights in this scenario must fit in the last case that I described. For a game featuring area lights, the shadowing model doesn't seem to match it since a falloff from umbra to penumbra is seemingly absent ...