Adding more bits just reduces quantization noise, so it only helps if the quantization noise is above the actual sensor/amplifier/ADC circuit's noise floor in t

Adding more bits just reduces quantization noise, so it only helps if the quantization noise is above the actual sensor/amplifier/ADC circuit's noise floor in the first place. The D810 for example can slightly exceed 12 bits when used at very low ISOs, <200. If Sony has managed to make an extremely low noise sensor here then there can be some benefit.