The ACARS thing is a red herring. The QF crew got the message at 2148, just after they got to top of climb out of Sydney, plenty of time to cogitate on it before getting near ADL.
I agree with the sterile cockpit policy re ACARS. Dings or buzzing printers during the takeoff are not good. If the company has a critical message to pass, they can do it thru ATC.