I think the idea is a little bit foreign to martial artists that study other arts. Take for example the various karate styles, even those that came from common (relatively) ancestry such as Seidokan Shorin-ryu and Matsubayashi Shorin-ryu. They have different syllabi, perhaps with more shared than not, but there's sufficient differences as well as an overall VOLUME of material that it makes the idea of a small federated subset of learning such as the KKW requirement, to be odd in conception to people who used to the other way of doing things.
I think now things are easier, with the vast information available on the internet, but back in the day, it certainly was not easy or simple to learn taekwondo, particularly taekwondo sparring. Back in the day, no one shared what they knew and if someone knew something, they kept it to themselves. It was incredibly difficult to gain any sort of conceptual information on what to do and how to do it, much less what fit where. It took a very long time to understand conceptually what kyorugi is about. It is certainly not something that can be learned overnight. That is just one small example of something within kukki taekwondo that looks easy, but in reality is not. It is a relatively simple matter to access the relative skill of a practitioner, in a minute of sparring at a test for example. If someone doesn't understand the modern training methods and modern sparring methods, it will be glaringly apparent in that minute.