That post doesn't read so well so i'm not 100% sure what you mean. The point of holding up a transluscent disc is the whole thing acts as a large light source, for soft light.
If you're telling me that the ONLY factor contributing to a light's softness/hardness is the size of the light source, then why would you have an assistant hold up a translucent disc, for sunlight to come through onto your subject? That doesn't make any sense to me. The transl. disc sure isn't making the sun a larger light source in order to soften the light. Wasn't your point point a few posts back that the omnibounce doesn't soften the light when its not bounced off walls/ceilings because it doesn't increase the size of the light source? Thats the way it read.
With or without walls & ceiling, firing your flash through a frosted piece of plastic is going to change the way the light hits the subject, more than likely softening the light. Are you telling us that is not true in your opinion?

