I work in Finance, and when I was on a H1B visa (back in 2010), the immigration officer asked me some bond-related questions, just to see if I had any clue.
They also asked my wife what I was working on.
It's pretty annoying to feel that you're not being trusted, but yes, they don't trust you.
Also the fact that he's Australian is a reassuring proof they don't base these question on color of skin...