You do realize that Hardening and invisible Haki isn't the same thing right? Applying Hardening to something, is completely different than flowing invisible Haki into it. When Luffy is training, we see him already Hardening his hand, and Hyogoro is telling him to let the Haki flow into his fist, which is already coated in hardening. We then see swirl patterns take form around Luffy's fist, which indicates invisible Haki.
Next we see the first panel, is normal hardening, the second panel, is invisible haki flowing into Luffy's hands.
With Rayleigh and the Boa sisters, they don't even use hardening with it. It's just invisible haki. Same thing with Kinemon and Kiku...
No hardening, just invisible Haki.
So please tell me, since you so adamantly want to argue that Ryou is a very specific Haki type, and not just the universal terminology for Haki in Wano. What pray tell, do they call Armament Haki then?