Not necessarily. In a pivoting ocho (back or otherwise), there is dissociation (twisting) going on, certainly. But for milonguero ochos, then no. The feeling with milonguero (crossing) ochos is of the hips staying parallel to the leader, but with one side or the other "sinking" or lowering as you stretch the side of the body to take that back/side step with the free leg. This sounds like two different concepts going on. If you're considering dissociation to be the separation of movement between the pelvis and upper body, then that happens all the time. Obviously. There is no way to walk and move the legs and hips while maintaining a smooth, constant contact in the embrace without it. I have never heard this use/definition of "dissociation". When talking about walking comfortably outside (meaning outside partner? as opposed to in line?), then yes, you have to use dissociation...of the rotational sort.