I think your personal perspective is dealt with in the first two paragraphs of my previous post.
Well I can certainly understand why you'd think that based on my post, but you're wrong I think.
I'll elaborate and explain why I think that (boredom warning, sorry can't be helped). I spent a year studying biological classification at the Natural History Museum in London. There is probably nothing more convoluted, complicated or blurry in its essence than a species, there are hybrids, there are sub-species, convergent forms, out-groups, physiological classifications, genetic classifications, cladistics versus phylogentic points of view. All to be considered when deciding what the official name of a species should be. As an example to show you how befuddling it all is, consider that the Orang Utan has two recognised sub-species (Bornean and Sumatran) these two sub-species are genetically more distinct from one another than Humans and Chimps, and humans and chimps aren't even in the same genus, let alone the same species. I still don't know what that's all about except to say that an illogical exception seems to have been made for great apes and chimps should probably be considered to be very primitive humans (and therefore be bestowed with all legal human rights).
In the course of my MSc studies I came to the conclusion that there simply is no such thing as a species, it is an invention of the human mind (I'm by no means the first to argue this point, Darwin refused to define a species in his famous work for some of the reasons I've already mentioned) for us to use and communicate with. The human mind has a nasty habit of pigeon holing and classifying parts of things which are actually continuously varying phenomenon. It just seems to be how our brains work.
Taxonomic names also take after a defining criteria. Ever see a name like Lutra lutra
or Meles meles
? These are examples of the genus being named after its defining species (in this case otters and badgers respectively), in other words someone said that all animals that look like a badger belong in the badger group. Just as someone said all throws that look like this belong in a kokyu group. Now maybe they were defining it by what it looks like on the outside or maybe they were defining it by what it is on the inside, either way is valid depending only on the importance placed on various characteristics. So, just as one taxonomist may argue that a specific feature of a claw is a more important characteristic than something else, you can argue that Mike Sigman's interpretation of kokyu is a more defining aspect than something else. Ultimately though, there is never any right or wrong, there is only opinion and more learned opinion, and its up to you to decide who you think is the wiser when talking about these things.
I think kokyunage and other terms are similar issues. Just replace the word species above with the word technique. All aikido requires the use of kokyu as you said yourself, so in a sense all aikido is kokyunage. It only depends on how you choose to label things. You can call it kokyunage even if it has no kokyu in it as it is in the end only a label. Just as if I felt like it, I could call you Susan instead of Mike and it wouldn't change who you are. If however you wanted to learn kokyu, well that is a different story, and you'd probably find your use of language changing to accommodate your newer understanding. But even then it still wouldn't be any more than a convenient label. If you want to communicate kokyu as an idea then language becomes more important, but that's not a function of the label, it's a function of the context in which the communication is taking place. Talking about kokyu in one of your workshops would be more meaningful than talking about it elsewhere, but there is no reason you can't use the same label elsewhere, just depends on what you understand by the word kokyu. If you know more about it it'll mean more to you. If you don't then its just a bit of Japanese that means throw the guy like this.
Labels are labels alone, they are not the essence of the thing they represent, just a convenient tag for enabling communication between people. The sky is blue because we've chosen to call it blue, no other reason.
Apologies for the waffling on. Its an interesting question just not sure exactly how to answer it effectively at present