Quote Originally Posted by deker
Quote Originally Posted by Полуношник
Do any grammar books share this approach?
I don't have any approach to it, just tried to understand. I wonder how it possible to learn a languge where the main rule is total arbitrariness.
An additional variation of the accusative case doesn't make things easier. You are going to make an "arbitrary choice" between these to variations instead of two cases. Additionally you are going to learn that ad-hoc sub-accusative case which is distinct from the regular accusative and indistinguishable from the genitive.

Do you study Russian? I thought you are a native speaker.