The opposable thumb and a big brain enabled our ancestors to survive in the wild. Key to their survival was tool building. It went from fire hardened wooden points to stone tools and eventually through the various metal ages. The progression was always towards better efficiency. In some styles of Karate, we see a regression rather than a progression in the use of hand technique, te waza. Of course, our understanding of karate is that it is an art of unarmed combat; however, this is no reason to believe that through effort and a casual disregard for physics and material science we can transform our bodies and hands into shields and spear points. This kind of thinking, to me, suggests a misunderstanding of kata bunkai.
The nukite in Pinan sono ni is often explained as a spearhand strike to soft body parts of the attacker: eyes and throat. First I would ask, what is the significance of teaching eye jabs? The Three Stooges, if you are familiar with these exemplars of slapstick comedy, demonstrate the simplicity of the eye jab with only two fingers and no training, and yet we have karate masters stabbing pots of gravel, bundles of bamboo and other targets all in an effort to transform multi-jointed fingers into a stabbing tool. Neanderthal man might ask, "why not just use a pointy stick?" A pencil is handy enough. Also, if empty hands are the only tools you have, why run the risk of jamming your fingers if you miss a soft body part and hit something hard?
I am pretty certain that in most cases spearhand strikes are not strikes at all. Jab an eye if you must, but stabbing pots of gravel in preparation is overkill. In the case of Pinan sono ni, the nukite is preceded by an open-handed block. The movement is strikingly similar to the Kyokushin's mawashi uke. So what's the point of the nukite in Pinan sono ni? My suggestion, an entry technique. The downward blocking hand parry's or slaps down the opponent's outstretched arm (presumably a punch or grab), the "nukite" traps, controls, grabs whatever it can. The open hand is open to whatever tactical opportunities present themselves, and not, I would argue, so that the finger tips can stab. In Pinan sono ni, the nukite is immediately followed by a turn of the body. Pay attention to turns in every kata. To me, they suggests throws, particularly when you consider what the hands are doing in the kata immediately prior to and after the turn.
Coincidentally, Te Waza in the Judo world refers to throws precipitated by hand motion. My favorites include ippon seioi nage and tai otoshi. There are many other throws in Judo, all involve turning, precise hand and foot placement, lowered centers of gravity, kinda like kata, only the emphasis is on optimal leverage rather than esthetics. Striking? That's the simple stuff in kata that hardly need elaboration.