At a certain level we are just talking about terms so no harm, but I am wondering if you take functional ki uses/ki power as subsumed under "ki-ryokyu" what then would "kokyu-ryokyu" signify as we have been discussing to this point?
Kokyu power is just Ki power with an additive... i.e., it is still ki-power. "Reiki" is sort of "full-blown ki but indeterminate about jin power". So you're right, it's actually a terms discussion and not much more.
The confusing thing to most people is that "ki-power" or "ki" is an umbrella term that covers perhaps too much territory. When Tohei stands solidly against a push, he calls it "ki strength" or "ki power" ("ki-ryoku"), but I would call it more "jin", since I attempt to focus/clarify a bit more.... regardless, we're talking about the same thing. "Ki" is the generic term... so the "ki-ryoku" is *probably* (IMO) derived from the functional usage of ki power and is not meant to be only "spirit" (although by extension, "spirit" can be a part of "ki").
The flippant answer to your question about when "kokyu-ryoku" is used would be to say, "Oh, you're talking about Aikido". What I would mean is that various arts call the same basic power by different names and if nothing else, that simply indicates how many centuries this sort of skill has been around.