The phenomenon oft the language that is traditionally used to transmit knowledge in the context of CMA, Daoism, Buddhism, Shint˘, ... aikid˘ ... has been studied scientifically at great length.
I think what you understand as imprecise, vague or ambiguous actually was intended. This language is a vehicle of transmission of knwoledge in itself. It is my actual experience that most important parts of the transmission get lost when it ist "demythologized" by converting it's meaning into only physical aspects.
Sometimes. Don't assume that all obscurity is intended to be convey knowledge, though. There are koans, yes. But there are also a lot of cases, especially in the martial arts, where obscure language was chosen precisely to hide the true meaning from outsiders. Even if the school's scrolls were stolen or copied, they would be meaningless to someone who had not received direct transmission from a master.