AF at Wide Angel distinctively unreliable?
Common sense. At medium to far distance, and with wide angle, your focus subject is going to be smaller than the AF sensor area. The sensor isn't entirely sure what to focus on - your intended subject, or whatever is behind it in the background.
It's not just common sense, though, since the note on p. 36 in the D3200 says as much.
Basically, any DSLR is going to have this problem with wide angle lenses.