I would assume that Etihad will process the tests and interviews with the EU, and based on how many pass/fail that stage, would directly correlate to the number of "yes/no" that NY, JNB and SYD will get. Since if I recall... 50 candidates were to be selected this year, so let's say if only 10 got accepted in EU, then they'd be handing out more "yes" emails to the rest of us, no?
Remember, that there is a security clearance, so say you have a criminal record, they may just say goodbye without having you going through the physical tests or whatever they'll be assessing in Stage 2.
Just my assumption.