Joe, you might be interested in one of my past blog posts: /blogs/tilting/2015/05/29/whats-in-your-feature-class-nothing-null-or-empty . The fact is Esri doesn't consistently handle missing or empty geometries. When a geometry is optional and missing, some tools leave the SHAPE field NULL while others create an empty geometry and insert it into the field. Even on the retrieval side, different tools handle empty geometries differently.
Just like an empty set is a valid set, and actually a critically important set in mathematics, an empty geometry is a valid geometry. Esri's poor support and handling of empty geometries is akin to having them support Roman numerals instead of Arabic numerals. Who needs to use zero, right?
From a practical perspective, I tell users in my organization to make geometry required when working with Esri's systems. Even though an empty geometry is a geometry, most users have no idea how to make them, so requiring them prevents some of the inconsistent behavior when there is a missing geometry.
