It makes no sense in this context but I also understood "Master" as another term for a teacher, a very good teacher. Not necessarily the best in the world at doing something but at least very knowledgeable and willing to pass it on, and competent at teaching. Teaching is a skill in itself hence the reason some of the best players do not make good coaches. There will always be great players who are great coaches but they are the exceptional exceptions who could probably be airdropped into an unpopulated wilderness and somehow hand build a badminton court out of trees and leaves then train the indigenous wildlife to play in less than 3 weeks. Maybe being a recognised "master" is being demonstrably, consistently masterful at something over an amount of time. Like Michelin stars for the best restaurants. Not all restaurants want to achieve the accolade, they can be a huge ambition and cost more to achieve and retain than is worth their investment. Greatness can be draining and very costly to maintain. Professor of stringing sounds better anyway, Professor Kakinami