I would concurr with Timelapse there. Stage 2 is structured, so everybody gets asked the same questions - and there isnt really any interaction with the HR assessor.
In stage 3, the questions that you get asked depend a lot upon you. Both the HR assessor and ATCO interview you at the same time, so they are both assessing the answers that you give to one or the other of them. Many of your questions are likely to based on information that you have already given them, such as your online personality questionaire, so are individual to you. Also, depending on how
you answer a question, depends on the question that follows - so you could say that it is quite a dynamic interview.
Hope this helps - best of luck!