Dxomark "measured" ISO vs Manufacturer ISO

What it does show is that ISO 100 on that camera is truly an "expanded" ISO and that ISO 200 is its base ISO.  The adjustments to make ISO 100 work are done in camera via processing.  The end result is the ability to use a "lower" ISO as well as the appropriate camera settings while still retaining a good exposure at the expense of either a loss or no improvement in dynamic range.  Your dynamic range shifts to the left or becomes compressed as a result.

You see the same thing occur on the D600 and the D800(E) between ISO 100 and ISO 50.

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Paul