Yes, Oh Do Kwan was a 50's creation but so was Taekwon-Do at which time Gen. Choi was moving away from Karate. This is evident in the 1965 book. TKD technigues were performed with both arms whether blocking, punching, or striking. With Karate,in some cases, one hand would perform a technique while the other stays stationary. The stances were no longer long wide stances and knee spring was implimented. Now this only pertains to Taekwon-do under Gen. Choi.
The name Taekwondo was created in the 1950's, but at that time, the technical biomechanics were still from Karate, and also Kwon Bup. And during the 50's General Choi was busy being a general in the ROK Army; he had no time to be wasting on taekwondo's development. He had no students and was not developing anything, at least in the 1950's. If you want, go look at the videos on youtube to see what Taekwondo looked like in the 50's.