This sounds a bit weird. I speculate the reason is that Genex...

This sounds a bit weird. I speculate the reason is that Genex are unable (due to Australian Energy Market rules) to operate Kidston as they would like. For example, I'm sure they would like to be able to use power from Kidston Stage 1 to pump water from the lower to upper reservoir, and to do this "behind the meter". This is not currently allowed by AEMO rules however - they can only do this by generating solar power into the grid, and buy it back again into the PHES. This means they have to pay network costs for both the exported and imported power. Until this issue can be resolved (assuming it can) maybe they're looking for an interim solution that is enough to get them to financial close, and can be undone at a later time when network rules are more flexible (Kidston is not the only project suffering this problem - Hornsdale wind farm and the associated Tesla Big Battery are also in the same boat).