Yeah he didn't know the names of the concepts that he already knew. My intuition says music theory is the understanding of the concepts, not the formal study of the names. Like a person that can only play the major scale because they studied the theory, in my mind they have less mastery of theory than a person that can compose "Little Wing" or "Lenny" without ever studying it.

To me, the theory is as much a communication tool as a knowledge. It is a common language for musicians to communicate musical ideas, at a higher level than musical notation. E.g. I can go to a jazz open mic, someone says the progression is "ii V I in Dminor", or a blues jam and its "I IV V, A major", or a Grateful Dead-type jam and its all mixolydian in B, and everyone is on the same page out of the gate. The theory is you know all of the scale modes, AND what they are called, AND can tell another musician what you're doing and why. Tons of people can play interesting things outside of the box, without know why or how it's defined.