Beijing wants it to remain a simple sovereignty dispute because it has been steadily changing the facts on the ground so that the dispute becomes ever harder to resolve in favour of the Philippines - or any other country China is in dispute with.
It's rejected"third party"views - such as courts ruling on international law - because it prefers to negotiate directly with its rivals,denying these smaller contestants a level playing field.
This would be the new world without a rules-based order. As a middle power,Australia relies heavily on the rules-based order and has a particular interesting in making sure it's maintained.