True, but the geek inside me still enjoys these theoretical discussions.
From my point of view, as long as your ADC has significantly more gradations than the DR of the camera (e.g. "16 bits" for "13 stops at pixel level"), this is a non-issue: you have an ADC that has enough gradations to actually capture the read-out noise of your image, so that is your limiting factor.
Say you have a sensor with full well capacity of 20.000e-, and read-out noise of 2e-. Your DR is 20*log10(10000)=80dB, or 13.33 stops. I guess the D800 sensor is pretty similar to that.
Tie that up with 16-bit ADC, and you have absolutely no "lack of gradation" issues whatsoever: you have to count electrons, the most you'll find are 20K, and you have 65K gradations at your disposal. Even with a 14-bit ADC, you wouldn't have terrible issues: 20Ke- to count (max), 16K gradations to use; the 2e- read-out noise is still your bigger problem.
D800 2.7e read noise FWC 44972 = 14.0 stop