Squawk7700:
In my head it seems to work like this and has always worked well for me
CaptainMidnight
ERSA GEN FPR section 5 covers the preferred flight planning in the Melbourne area, including VFR overflight of the ML CTR.
This is what I remember too from when I did it, but these guys seemed to have set up for this exactly and had the clearance denied.
I suspect they were trying to do CTA navs and have a box that needs to be ticked in the syllabus. They probably paid ~$1000 for the nav and will have to try again another day. They might have waited a number of weeks to get weather where 6000+ over Melbourne was possible.
It's easy to deny a clearance, but it can have a big impact on the requestor. It's not necessarily just the minor inconvenience of diverting OCTA.