At an advanced level, Vaughan assumes you know the rules. They don't care if you can conjugate "to run." They care if you can use "to run," "to run into," "to run over," and "to run out of" in a split-second decision during a heated debate. If you are an advanced learner, you have a specific problem: The Passive Filter.
You understand English perfectly, but your mouth has a filter. You translate in your head. You look for the "safe" word instead of the exact word. Curso de Ingles - Vaughan 4.0 - Nivel Avanzado ...
You are no longer a beginner. You are not even intermediate. At an advanced level, Vaughan assumes you know the rules