there are some masks that also go with the bone and blend/morph/key shapes you can see in the pc version how the normal maps are used with these masks so you will move the forhead bones bind the correct key shape to the bone movement that will wrinkle the head and the RGB map will also be used to show the part of the normal map that is rellivent to the animation giving better visual of what is going on showing the shadowing caused by the head wrinkling
There are three extra textures and three extra normal maps that get masked to do this on top of the key shapes that only give a very subtle effect helping the bone movements look more realistic
Yes there are a ton of bones in the face but you can hide each bone in pose mode so you can see what you are working with the bones are in groups the root of each group will move every bone in each group reference the UE4 face rig to see what ones do the animating and what ones just get used to form the shape of the character
remember this is not a finished product there will be a set of creation sliders that will probably be using the extra bones to puff out the lips change the type of nose etc
its not easy to reverse engineer something … when its not finnished it’s even harder as you don’t know what your supposed to be making GOOD LUCK