Do kata contain secret techniques, not visible in the execution of the kata ?

In Saifa the 2 time double punch right after mae-geri is changed from the original technique, kaiko-ken (crabshell fist). Is this a secret teaching? The angel in wich kaiko-ken is delivered onto the ST18 is significant to obtain optimum effect (burning sensation below nipples and a sharp penetrating pain, opponent tends to 'collaps' inward losing power in schoulder, chest and arms).

I was told that all kata have these secret techniques, however I was only thaught a few in that way.

Any of you have knowledge of these 'secret' techniques ??