Cropping will always reduce photographic dynamic range (as defined by Bill Claff) due to magnification of noise when final total print size is the same. There is nothing special with D500 here. Similar with DX crop of an 800 series image which will be closer to the D500 dynamic range. However the crop will not change what happens at pixel level.
I was about to write approximately the same sentence. With 1.3x crop mode on a D500, pixel count will be reduced fron 20.9Mpix to 16Mpix, sufficient for most practical uses.
Additionally, using crop mode instead of a teleconverter will not cause any f-stop reduction, a very welcome feature.
Ciao from Massimo
