I was out using the 2.0 firmware today and I wanted to pass this along...
It looks like the behavior of subject detection with the Wide AF areas has changed. Normally, when you have a wide AF area, if it's anywhere on a recognized subject, the camera will go for the body, face, or eye.
WIth that in mind, I tried the Custom Wide AF area down to a single point. When I pointed at a gull's face, subject detection easily found the eye. However, when I moved the AF area away from the face, it gave up the eye and it appeared subject detection simply allowed the Wide AF area to work as normal. When I've done that test in the past with the Wide (S or L) area, as long as I had pretty much any part of the bird under the AF area, it still went to the eye. Now, you have to have the eye either under the AF area of very close to it.
I thought maybe this was due to the size of the AF area so I payed with that. In every instance, when the eye was out of and just a bit away from the Wide AF area, the camera wouldn't keep on it anymore (sometimes it would go for the body if the body was under the AF area, as expected). I also tried this with the normal Wide (L) and (S) areas with the same results.
I tried this on a variety of targets and found the same thing happening over and over. It seems like they made a change to the way this works.
However, if that's the case, I think it was actually the right move. I've had all sorts of trouble with subject detection focusing on the wrong areas of the target even when I had the wide AF area where I wanted it. I think this will actually improve my overall keeper rate.
Anyhow, I wanted to pass this along and ask that if you have a chance, test and see what happens. I'd like to try to confirm what I'm experiencing.