I've got an ATPL and an engineering degree. But thats not all that relevent, I simply don't think the response to the original posters question addresses what he or she asked. I think they want to know if, in a balanced turn, the angle of attack is the same for both wings.
I still don't understand the reply. Do you mean the angle of attack with respect to the airflow component parallel to the lateral axis as per your diagram? Or is this a representation of the angle of attack with respect to the free stream?
If its the free stream, then I don't agree and I don't agree with the parallax demonstration by Mr Williams either. The reason the parallax arguement doesn't work is the free stream presents itself to the wing from a direction which is parallel to the trajectory of the aircraft. So if you close one eye then look from a point half way down one wing you are assuming that the free stream is approaching both wings from one point. Which it clearly isn't.
By the way, I agree that a roll torque is applied if there is a sideslip and thats what gives stability in roll about the longditudinal axis but I dont think there is a difference in the angle of attack in a balanced, zero slip turn. I'm happy to be proved wrong but not by answering a different question.