While I agree the 2/3 steps faster is useful, I significantly disagree that f8 is too slow with Nikon ML cameras.The 400/4.5 is 2/3 stops faster, so while not ground breaking difference, it is still quite much. Especially when TC1.4 is used, because f8 would be too slow most of the time unless shooting in very bright day light.
There is negligible loss of quality at 1600 ISO – and thanks to Expeed 7 better control of noise than we say a D850 at a similar enhanced ISO.
Taking the leopard photos as an example, assuming using a beanbag from an open top vehicle there is slight loss of sharpness on the left ear e due to loss of depth of field in the crop images. f8 could have helped.