And it is not only about painting brushes. Other brush-based tools like "Eraser" also 8 bit only.
"Remove Brush" and other similar cloning tools partially affected by this problem. Here is example with soft "Copy Brush" in 16 bit. Gradient cloned in the middle is true 16 bit, but in the soft edges of the brush gradient start to show 8 bit banding artifacts.I do agree however that it is essential that there is a way to stamp 16bit large textures. I don't recall exactly, but I believe the stamp tool retains full 16bit/32bit values?
So currently if we edit large spots on 16 bit photo with soft "Remove Brush", we introduce 8 bit areas around those spots and so permanently damage 16 bit image source.