Okay--- a little further digging. I teased out a single basic form that would take me across a range of arts and time frames. In this case its Pyung Ahn (aka J. Heian; aka O. Pinan), the 5th of that series.
As performed in TKD and TSD (See: Kang Uk Lee) there is a sequence at the end of the hyung following the jump in which the practitioner backsteps into a Half-mountain stance, thrusts forward and again retracts into the Half-Mtn stance. This same sequence is seen in the Japanese version and in the Okinawan version. However, in the Japanese and Okinawan version there is a simple turn and a juxtapose of the hands which bring the person from left Half-Mtn to Right Half-Mtn where the sequence is then repeated. Only in the Korean versions does the person shift from Half-Mtn to Mountain Posture, then turn, go directly into the thrust and retract into a Half-Mtn stance.
Since the J and O versions do not use the move there is no help with analyzing this movement from where they are concerned. The Korean version holds with the previously mentioned interpretation (simultaneous, double block) which is admittedly pretty lame.
For myself I am left to ponder why the Koreans would see fit to add a posture to someone elses form?
I do have a possible theory, but wanted to wait until other people had a chance to comment. Thoughts?