Comment by timschmidt

It's been pretty clear in my experience that experts tend to be capable of working with the same ideas in many different forms. That's what I would call mastery. It implies "complete" knowledge, which probably means several interrelated encodings with loci in different parts of the brain. Those interrelated encodings will be highly associated, and discerning in an expert. Which implies a high degree of usefulness and specificity in communication. This matches my experience.