The thing is, the info on his AIF papers is info HE provided, so it is first hand info. What info did he provide on his marriage cert? I understand that he would have given his place of birth, his age, his occupation, and details about his parents to the clergyman for inclusion on that document too.
First hand info is usually more reliable that second or third hand info. But do you know why he would have given incorrect info when enlisting, despite giving his wife's details as his next of kin... To me it does not make sense to give correct info for n o k, but incorrect info for place of birth ... particularly as you have his birth being half a world away....
Cheers, JM