Shimbori-san explained that this is a build still in development, but breast physics have not been removed, and movement is indeed there. In Dead or Alive 5 breast physics were very exaggerated, and for Dead or Alive 6, the development team is aiming to achieve more realistic physical effects.
As we already know, the Soft Engine isn’t being used for this game and has been replaced with a new one that is being developed at Koei Tecmo. Yet, since it’s still in development, it’s not ready for general showing. Gameplay is being showcased just to show the progress being made.
The Soft Engine is being replaced because it was old, and the new engine doesn’t yet have a name. The development team is working very hard on it.