As the map below shows, the vast majority of Australia’s best PHES sites can be found on or near the Great Dividing Range.
I am guessing, about 90+% of our population live within a short distance from the range.
The Great Dividing Range is 3500 kilometres long.
Given those demographics, you would have to think GNX will be looking for suitable sites (for generation and storage) that are in close proximity to the Great Dividing Range.
The acquisition of the Jemalong site would be in keeping with that strategy.