Why does it matter how many AF sensors work above f5.6? Sports and action shooters almost never shoot above f5.6. We can't get enough shutter speed at those apertures to stop action, even in direct sunlight. I would imagine the same would apply for wildlife, which moves and tends to be shot at long focal lengths, as well.
And, for things that don't move, like landscapes, portraits, still life, photo journalism, macro, and such, FX is a better medium than DX. Even if you prefer DX for those subjects, one sensor will suffice because you can focus and recompose.
Besides, I thought all lenses focus and display at their maximum aperture? How many lenses (and how many pro lenses at that) are smaller than f5.6 at their max aperture at any focal length? Maybe there is a teleconverter issue, but at those extremes, is IQ a bigger issue?
Maybe I'm missing something, but I don't understand why the number of AF points that function at f8 and smaller is a big deal, except perhaps in very rare circumstances.