If the separation minima applicable was 3NM or 1000 feet, it would appear that the incident took place within the jurisdiction of the Sydney Terminal Control Unit.
The controllers there are the biggest bunch of lazy, overpaid, prima donnas in the world - and believe me, I have seen some prima donna controllers around the world.
When TAAATS was implemented way back when, every controller in Australia was happy to go with the HMI that was proposed [and as amended based on operational trials etc] - but NO, not Sydney controllers. The HMI wasn't good enough for them - they had to have a special system partition built so that they could use the equipment the way they thought it should be used.
There is NO excuse for 'adjusting' the HMI layout individually in a highly specialised environment like a TCU. Adjust the seat height - adjust the volume - but DON'T ajust the primary functionality and display characteristics - there should be absolutely no need.
It would be like a 747 driver changing the display settings on the 'dashboard' because he/she doesn't like what the manufacturer installed.
The controller concerned should be severely caned, and management at SY TCU should be hung out to dry for allowing such prima donna behaviours!!!!!