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.
In that case, everything is Aikido and there is no right way to do it. That's the problem with your relativism... you don't stop and think what the full implications of it are. In fact, there is no such thing as "Aikido", it's simply Daito Ryu, if you want to go by the trendy idea of relativism.
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
It's pretty simple, despite all the attempts to say "everything is kokyu; it means what you want it to mean", etc. Either you know what kokyu is or you don't. Tohei's "ki tests" are classic examples of the core of kokyu-ryoku... that's why he teaches them and why they are considered the essential of Aikido technique. But hey, I'm quite well aware that a lot of people don't understand that fairly simple point and are going to argue without a care to what the argument does for them in the public arena. I think that's as it should be, TBH.