And little ATSB discussion on the time required to secure and brief the approach. They were so close to GEL that they would likely have had to hold (I'm not F100 rated so not sure how how long it takes to run the EF checklist and brief).
I'd imagine the time delta between touchdown and Perth and GEL would be just several minutes by the time the holding to prepare the GEL would have been taken into account vs doing it enroute to PER.
There were definitely some decisions that were not optimal, but if the time delta was indeed a few minutes, I don't think deciding to fly to Perth was necessarily one of them.