[davidmanze]

You can't see the difference between 60Hz and 120 Hz timing wise.You do not lose any bird with a 60Hz feed, the frequency has nothing to do with your proposed... delay. A strange idea to think that 60Hz somehow makes you lose birds in the frame of the view finder.... The latency you mention had to do with the arrival to the EVF of the whole video stream, not the time between frames.

To illustrate: if you test your reaction time, you can see just how little 1/60th of a second is, let alone half of it (the difference between 1/60th and 1/120th).
I tried this website test once (casually), to see what my score would be. It was around 0.35 seconds. So, about 1/3rd of a second, or 3Hz. 60 / 3 = 20 times longer than what 1/60th of a second actually is, or 40 times bigger than the difference between 60Hz and 120HZ.
http://www.openphotographicsociety.org/shop-and-tools/calculators-and-utilities/time-lapse-calculator/human-reaction-time-test

Why then a higher frame rate? Because, at certain exposure times used by the live view, the feel is more smooth. And, if the live view feed frequency is directly coupled to the read out of the imaging sensor, you get more image/PD data to calculate AF needs.

    You missed the point again BC muddling the picture with human reaction times  ...... this is sports world @20-30 IPS .....  no single shots here
 ........ the only human reaction time occurs on the initial shutter button press ....... after that the camera rattles 20 IPS while you pan ...... any human reaction times not playing any part at all  .....
 It's clear you only take one shot at a time BC ....... whereas I might shoot 30-40 images with out letting go of the shutter button ...... in fact I rarely shoot one shot at a time ...... only the first one has any human delay ...... surely we are agreed on that ??

  I'll leave you to consider your reply to this part of the discussion ...... because if we are not agreed on that we be will going nowhere !! ........