fender
This "system" has been happening for years on many international inbounds, eg:
NRT/SYD/MEL
SIN/DRW/ADL
LAX/MEL/SYD
DPS/MEL/SYD
MNL/BNE/SYD
NRT/CNS/SYD
SIN/ADL/SYD
I'm sure the Australian Customs experts are pretty aware and in control of the situation.