" Will the same dynamic apply in deep descent ? "
In short, yes it will. As long as the wheel is turning you can generate a braking force pretty much. You still need a mechanical brake to hold you at a stop although you could use the motors as trying to reverse up the hill in that case to hold you at a stop. It would use power and generate heat so it's not ideal but you can see how finely and accurately you can tune an electric motor drive with electronics and software as compared to a electronic over hydraulic/mechanical one.
Don't get me wrong, modern traction controls are great. Probably bat above their average actually considering the mechanical limitations. It's demonstrates how good programming can achieve so much.
Electric drive is just the next level in that regard.
