The problem is dynamic range is subjective, seeing as the definition of dynamic range (at least in terms of sensors) is the difference between the brightest and darkest details the sensor can record.
Dynamic range ultimately comes down to how dark you can go before all discernible detail is lost to noise. The benchmarking site DXO-mark defines dynamic range as the difference between saturation of the photosites (which clearly limits the brightest thing you can record) and the point at which the signal to noise ratio hits 1:1, that is where the signal and noise are equal.
I believe DPreview also bases their figures on the shadow noise but uses a different higher threshold (which I cant find anywhere on the site) which is why their figures don't match up.