Progress and autofocus speeds. D3 vs D7200

'Blazing AF' well most if not all DSLR's may be blazingly fast compared to us humans. The first AF system I saw was a colleagues Canon and I was a little sceptical about his claims for speed so we had a contest shooting several subjects at the same time. Result Canon = 10, Me = 0.

FWIW Sony claimed the worlds fastest autofocus 0.02 second AF speed with their α6400. What sometimes seems to be missing is the AF accuracy. Manufacturers want to put their best foot forward so their focus (pun intended) will be on their percieved USP. So this particular claim may be on a preselected single focus point rather than selecting a mode that includes many focus points and it may be when compared to other cameras using a different method that the gap is significantly narrowed. What happens to speed and accuracy with the same AF module between DX and FF?

As far as your Nikon comparisons go a good indicator may be the particular AF module used. With an underlying assumption that newer must equal 'better'. Does this offer any insight?
Nikon AF modules reference table - Nikon Rumors