Test for yourself via movement one of Heian Sandan/Heian Godan (Hidari chudan uchi-uke in migi kokutsu-dachi). Have a training partner push down your hidari chudan uchi-uke without the eyes and head fully facing in the direction of the technique. Next, make the correct position with the head and eyes focused perfectly in the direction of your uchi-uke. You will notice a very big difference. Likewise, use the same process to test the two kake shuto-uke followed yoko-kekomi in Nijushiho. Of course, this ‘kihon’ applies to all of the techniques and kata of Karate-Do.
While there are exceptions i.e. – movement 41 of Bassai Dai and movement two of Wankan, they have purposes that are less generic in application (such as kenseiwaza—feint techniques, and shikakewaza—set up techniques). Exceptions must be understood and applied when appropriate, however, they are secondary to standard techniques and standard budo methodology; what’s more, exceptions can only be maximized when the norms/standard-karate are fully grooved into the subconscious mind (thereby, allowing ‘appropriately reactive’ usage in freestyle).
Some will indeed be thinking about the three Tekki Kata now, and Master Nakayama’s comments pertaining to ‘sharp head turns’. This is an excellent example but, again, his agenda in stating this was greater than Tekki. To reiterate, correct head and eye position is a characteristic of the vast majority of Karate-waza: and for very good reason.