[senkora]

I would describe it as: natural human languages with native speakers eventually develop a grammatical way to complete the vast majority of incomplete thoughts that speakers tend to have.

So, if you know the entire language, then you can complete your thought. But if you only know the common parts of the language then you may need to start over with a different sentence structure in order to express your thought.

Maybe that maps to C1 vs C2? At C1 you can express your thoughts with occasional backtracking, but at C2 you almost never need to backtrack?