As with most anything in the world, karate transmission means new knowledge for many and lost intricacies for most. When a combat art is removed from its area of origin, it is natural certain elements will be either withheld or simply not taught, as the presumption of knowledge and understanding by the teacher to the student was misplaced or misguided. This is more a flaw of human nature than any real or perceived notion that certain aspects of an art are retained for only the closest student.
The taking of kuzushi, or balance, has been studied and discussed in great detail, most especially by judo-ka and jujutsu-ka. To off-balance an opponent is to gain control of his body and energy for the purpose of throwing or joint locking applications. This is not necessary if the objective is to simply punch or kick him. After all, it is not really necessary to off-balance an opponent if your intent is to punch him in the sternum or kick him in the testicles.
Disclaimer: if you do either successfully, the opponent will likely be off balance anyway!
Within Chito-Ryu and Yoshukai Karate exist kata showing the off-balancing of an opponent. Since I am of the belief that fighting is a game of millimeters, rather than inches or feet (no pun intended), it should come as no surprise that my focus in delivering an attack happens at a very close range with my opponent. Kata such as Chinto, Sochin, Ni Sei Shi, Sanshiryu, and Ryu San immediately come to mind when considering techniques specific to disrupting an opponent's balance and timing.
Oftentimes, I see sensei attempting to teach nage waza (throwing techniques) or kansetsu waza (joint locking techniques) from a distance entirely too far from their opponent. The first time a student resists the technique, I have personally witnessed a teacher applying power and force to the technique. Such increases in energy output are not necessary if the space between tori and uke is null and tori's hip placement is correct.
The exact same thing can and will be said for balance disruption. Jigoro Kano, Ph. D., the founder of judo, famously said, "When the enemy wishes to enter your house, open the door and let him in. When he wishes to leave, show him the way out."
Kano sensei's meaning was clear: Maximum efficiency with minimum effort. A throw, joint lock, or disruption should be executed with minimal output, but with maximum efficiency or devastation to the opponent.
Study hard, train harder!
