Im not quite sure what you are trying to prove or disprove. Without having handled most camera bodies or brands of cameras I would always assume that focus is never going to be completely accurate every single time, even manual focus on a tripod can miss focus if the subject just happens to move a little too much. But everything ive read from users of sony a7r2 and later generations all seem to indicate that missing focus has become increasingly uncommon.
It should be fairly clear after my couple of references to Gary Fong's video. I simply wish Fong, for example, had posted high res photo samples to go with the eye tracking thing he showed.
The few most recent posts here showing photo samples are more along those lines.
I happen to have a short sequence with eye AF, not 50 F1.4, but 106 f6.3, which surprisingly has less DOF than 50mm f1.4 according to DOFmaster. 1/6 oof( or camera shake) with a walking baby.... I'de say that's a lot harder to nail than posed adults.
That's exactly what I was hoping more people would show, including Fong, at Youtube. In these examples, it looks like the Eye AF is in the proximity of AI Servo focus for centering and approximating the depth of field.
But thanks .. and yes ... this fine-tunes the conversation much more than a little highlighted box on a youtube video.
What he posted wasn't technically a video. It was a series of 24mp photos shot at 20fps with eye AF engaged.
Fong posted video of video along with photos reduced to like 10% size stuffed in video format. Much different from what Dustin Abbott provides, enlarging 100% crops for Full Screen viewing, and posting additional to website.
It's worth noting what Fong shared in the video about AI SERVO and the tip of the nose, vs. eye tracking. When I shoot, I like to have the nose and eyes in focus with room to spare front and back. So whether a camera detected the nose (face) or the eyes may work almost the same for my needs.
If Eye Detect is no worse, and doesn't raise the cost of a camera more than a fraction, then it may as well be included.