I honestly don't understand this fascination with the exam changing from a B727 to a B767
It's quite simple. Adult learners like to see the relevance of what they are learning. If you can provide that, learning outcomes improve. That is, students learn more stuff and they remember it better. It's a measurable fact.
Now we all know that the content of ATPL Flt Planning has only passing relevance to real life. But if the aircraft is at least one that is being used in Australia, there is a certain interest along the lines of "I might fly this one day". Or at least "I might fly an aircraft like this one day". The B727 fails on both criteria; the B767 is arguably more contemporary and matches what's in the Systems syllabus.
The A320/A330 is probably the best option for the ATPL syllabus, not least because - I'm told - Airbus offer the technical specifications for free, so students wouldn't have to spend $50-ish buying the utterly & mindlessly irrelevant Boeing B727 book. (Whose pages are reasonably soft and quite absorbent, which gives it its one and only known use outside CASA.)