It would according to the T&C's - Dave Noble already explained why. I figure that AA knows the flight happened based on their codeshare, and passes the details back to Qantas. If AA didn't want to credit for a codeshare, then the T&C's would be updated to remove that ability.

If I was on that flight and it didn't credit, Qantas would end up crediting the flight to me based on the T&C's after I complained to them.

It's the same as a Qantas flight on Jal metal (or rather how it used to be before Jal joined OW). I'm yet to fly any AA flight not on AA metal, so can't give a concrete example though.