from what I understand the concept of ryou is to cover your blade with the haki in your body
if its done correctly , your sword cuts what you intend to cut and does not when you dont intend to cut it.
mastering this is also what allowed hyogoro create a barrier around his fist.
the process of creating a barrier is
having the haki within your body work as an extension of it. simply put its to allow your haki flow outside your body to your desired target. as hyogoro says here , you must let the haki flow from your fist to the parts that dont need it. here we also visibly see luffy's haki outside his body unlike before.
coa was a bit downplayed when the likes of kinemon and kanjuro coated their weapons in dressrossa. what a twist this chapter was, now folks think they have the highest level of coa which is this . what a turn lmao
I think mastering the barrier is the same level of mastery as having the ability to cut and not to cut with your blade (having your haki flow from inside your body to a desired target). penetration would be a step above that which is what luffy learned at the end of udon.