Dora-9 - I cannot find any mention in the definitive history of the Double Sunrise story (Qantas Empire Airways - Indian Ocean Service - 1943-1946) that says any Catalinas ever took off towards the NE.
Most takeoffs were done in the wee small hours, long before sunrise, when any Easterlies would have been relatively light, as I see it.
When a high pressure system located in the Bight is creating strong Easterlies (as in a normal Summer pattern), the strong Easterlies usually abate to a large degree in the wee small hours.
Quite a number of planned takeoffs were delayed due to rough water and strong winds - but nowhere is the wind direction mentioned in these cases.
Calm water was a bigger problem - and the writer explains how if glassy water was encountered, the extended takeoff run wasn't a problem, as "several miles of water were available (for takeoff) without any high surrounding obstructions".
This description indicates a Sth-Westerly takeoff run, towards Fremantle.
In a couple of accounts of takeoff from Melville Water, the writer remarks about "Fremantle slipping away underneath", after takeoff - and another paragraph speaks of "Perth appearing under our starboard wing as the aircraft banks to a heading of 315° towards Ceylon".
Nowhere in the book is mentioned any instance of a Wartime Qantas Catalina becoming beached at Como. It's possible this may have happened to another military floatplane at some other period in time.