I'll port this over here:
Depends on what you think, the "Soft Engine" is.
It's actually two different features. One is a subsurface scattering shader on the skin texture, for that warmer and softer glow of the skin (it's standard for every current console generation title though) and the other feature are more "bones" in the breasts, so that the movement animation is even more detailed and natural, than it was before.
Subsurface scattering is applied to every character (also the males) regardless of the boob mode, but the additional more natural and detailed breast movement you will only get in LR mode.