[davidmanze]

And care to explain why the 307,000 RGBIr pixels sensor is not designed for subject recognition?

Subject recognition, yes. Nikon has been doing this for ages, even with less resolution. Their 3D AF tracking is based on it (and works very well, btw.)

Face recognition: maybe.

Eye recognition: certainly not. The resolution to do that reliably (!) is simply not there. And there's one more glitch: even if the metering sensor properly detects an eye, there still needs to be an AF sensor at that spot to actually focus on it. With typical AF systems, chances are, there is none. And if if there happens to be one at exactly the desired spot, chances are it's too big to cover the eye only. Or, in other words, to reliably focus on the eye, not the eye lid or the lashes.

     Err ..... cuckoo surprise surprise !! ....... the D750 has "face" and "eye recognition" ..... and it works !! ...... Nikon never made claims for it ..... but it's there in "auto area mode" ....   


 Here's DPR's video from the D750 review:

 https://www.youtube.com/watch?v=wQ4rEvbCNuw&t=1s

  In fact I've just tried it again with the D750 ...... 
  .... "3D AF" uses the initial focus point to recognize the subjects eye; then locks and sticks to it as one would expect ....... 

........ Auto area mode finds the nearest eye "by itself" !!  ....... the video is using "auto area mode" btw. !!

..... the D500 also has it (just checked) straight to the nearest eye !!
  
..........  just like a Sony A9 ......

Check out your D850 ....... you may surprised, even delighted that you have what many thought was a MLC only feature !!

...... mst .......... now you have two DSLRs with eye detect ....... cutting edge stuff