And therefore all the more interesting!! So what's your take on that question?
A lot of it relates to the long standing hatred and out right racism the Japanese have had for the Koreans. Look at Mas Oyama, a Korean, who changed his name when he moved to Japan in order to be more Japanese. I don't see the Japanese teaching any more to the Koreans then to the Americans. In fact, there is such long standing animosity in the culture, it would probably make it down right impossible for a Korean to be accepted into the inner circles of Karate training.
This is why I think there probably isn't anything more to many of the TKD forms created in the Kwan era. I don't think they learned much more then punch/block/kick and were forced to cross train in order to round out their martial skills. IMO, this is why KMA curricula seem so scrambled. You've got all sorts of peices being drawn in from a number of different arts in order to fill in the holes. Sure, you can go back and reinterpret sections of forms that are similar to the classical hyung, but I maintain that the resemblance is probably coincidental.
Of course all of this relates to the topic of this thread. You've got information that is obviously being obfuscated about Karate through the 50s, 60s, and 70s. During this time, the hearts of many KMA's were forming and I do not think they had a clear picture of what karate was all about.