Perhaps it was a misprint that has subsequently been rectified since you posted.
Maybe, but I did a run through of the current Victorian entry permit for an orange zone and I didn't notice any section where you are asked or required to declare overseas travel.
Perhaps it has yet to be updated. But the way I see it, given the complete removal of any inbound requirements, flights are unlikely to be met by anyone.
Given the permit doesn't ask, who else is stopping this from occurring?
On a separate note, I've heard that by the end of the week Fri/Sat the Vic government is likely to make an announcement regarding our situation. Fingers crossed.