Now, I think it is safe to assume that Lin Yuantu was mentally strong enough to resist having KHBD/BXJF turn him into a crazy genderbender like DFBB. (since no mention of anyone in Jianghu or Lin family took any notice of him being weird).
He was also sane enough to put the decree that Lin descendants should not practice BXJF (probably understood that without his degree of training/monkhood experience, they would go nuts without their nuts.
Since Lin was already an accomplished martial artist, why did he not create or leave some better orthodox martial art for his descendants? He left them with nothing but a big reputation and a useless set of 72 stroke sword art. That's like a recipe for disaster!