I agree with you that some instructors for lack of teaching skills fall back to correcting the students with mystical terms. Instead of concrete corrections, and the the reason maybe the way traditional Japanese MA are taught. The instructor demonstrates with out saying much and you have to practice untill you get it. Some people will get it physically but not understand it intellectualy. If you can't verbalize what it is then how can you teach it.
I hope this post makes sense.
Words are only useful in the context of shared experience. I think any description of the body's subtle forces is necessarily inadequate.
The ancient classics tell us how to practice, but generally not how to conceptualize what is happening. Is this because the old masters were all stupid, or because they thought intellectual "understanding" of the practice was useless? Who am I to disagree? This is not merely a matter of culture, it is a universal truth.