It made me curious, do you have a verifiable reference (DVD, youtube video) on this?
BTW, I have seen Al social dancing at 2007 SF Salsa Congress and I was a bit surprised that his dancing looked even cleaner and plainer than on his DVDs and performance videos. I was very impressed. In addition, I could not notice a great deal of permanent shoulder action,... but maybe he was a tired at that night
Actually my instructors never really tried to improve my shoulder action during basic step. What I was consistently said is to focus on the upper body to follow my weight change which makes the torso shifting naturally left <-> right during the step, additionally the ribcage should follow the back <-> forward movement (subtly, naturally).
As to the shoulder movement, one of my instructors told that isolated forward rolling is very rarely needed, backward rolling is much more useful on occasion, but it is a good idea to practice both just in order to aquire better body awareness.
Thanks, Al Espinoza styling dvd 1 is where the shoulder movement is mentioned as Al said it looks cooler than backwards rotation. Cannot post clip as on the DVD.
Great point about the upper body though.
Thanks