Nikon RFs were based upon the Contax design, Canons were based upon Leica.
My father-in-law visited the Nikon factory during the Korean Police Action, he was in charge of one of the air wings in Japan. He was told that in addition to the availability of designs the engineers (optical and mechanical) who were in Japan for years came from both companies and stayed after the end of the war.
The USSR took a sightly different approach and focused on volume rather than quality. From what I've seen some designs that came from union have been masterful. In some cases from scratch, in others they keep the great and make it better.
I think we call the copies because that's the way they started out. As mentioned earlier much of the "NATO" aligned world hasn't had access to their products from the beginning.
B2 (;->