I get the sense that when Alberto is finished with his entry/blend that he is still facing opposite uke and the arm bar style lock on the elbow is coming from below, right arm on right arm. That is not rokkyo.
The problem I'm having is visualizing the tenkan from that position.
I could be way off base.
This is why videos help so much.
Ok I managed to get some video of this apparently unkown technique. I am sorry it is still a simulation but at least the movement can be seen clearly:
You may skip all the initial blabber and move right to minute 2:15 where the actual illustration begins (or, more exactly at 3:30, though at 2:15 it is explained what that homemade training device is, in case anyone wonders).
Since I first found it out, I have tried it in several trainings with actual ukes and it invariably works very well (main setback, as far as i can see: absolutely not
to try against an armed hand).