Two Chinese Pentax users posted at the Xitek Pentax Forum that they received an early production K-3 III which is confirmed to have the Eye AF function and the firmware has already been updated to V1.0 production version since 1st of March. One tester even posted the below viewfinder snapshot to illustrate the Eye AF does work, even with a flat displayed picture like this:
Besides, two screen captures of the K-3III's Info screen and its AF options are also posted: