What I think he meant with flexibility is useless/nothing by itself meant that he viewed his taji as an art that is concerned with self preservation. If flexibility does nothing to enhance your self preservation skills, then it is meaningless in his context. But if flexibility does enhance your self preservation skills(as in enhancing your taji skills) , then it is meaningful in his context. Hence the pursuit of flexibility by itself is meaningless in the master's context.
You explained it better than he did ! Flexibility is a core part of my Tai Chi training. Extra flexibility gives me extra range, extra mobility and better protection against injury. I've seen instructors that are NOT flexible so of course 'flexibility' is meaningless in their schools, hence my comment "If they can't do it, you don't want it". .
In fact he is very flexible. His joints have an incredible range of motion. He can rotate his elbow more than 180 degrees. If you can meet him sometime, he will show it to you.
In addition, flexibility is implied when you "open your joints". In this context, joints are gears working together. Having flexibility is like having sufficient lubricants between the joints.
Joe Blow He is not ultra traditional though - he tells jokes, he listens to and answers questions. I have trained with traditional Chinese masters who would have walked out of this session after the first question.
