There's no need to "see" - it has been made very clear to you there is one, and only one, correct answer which is that the flights are treated as an international-to-international connection, using transit security in SYD and baggage fully checked through ( to be collected and customs entry at MEL). Let's not confuse the OP with speculation about how it could be different in an alternate world, when frequent travelers and experts have already confirmed how it actually works.
It doesn't fit squarely into either category and whether not you are happy with the terminology, is not really important to the correct answer in terms of how Jetstar actually operates these flights. The important part for this discussion, is that the tag flight is *treated* as international - i.e. outside border controls - for all relevant purposes.
