You will have to forgive me, I have no experience of tendon and joint work in wing chun. You will need to explain how it is done and (if possible) what it helps with, and how it does so.
Regarding PB avoiding the training, I think you said it had something to do with huen sau movements. PB does these, as does everyone else, so are they doing the joint/tendon work without knowing it or do they need to know what they are doing for it to have any effect? If so how does this work?
Thanks