Thanks for the video post Graham.
I don't know what "take their shoulders out of their sockets" that Geraldo posted refers to. Sounds painful. The beginning of the video Graham posted looks pretty much how we practice the exercise, though we use it more for ki development than technique. A characteristic of the exercise is that uke feels like he's pushing into an unyielding object throughout the entire exercise even though nage's shoulder is retreating during the initial phase of the movement.
We have a lot of paired exercises where nage moves while being pressured by uke via pushing or pulling.