This guy also says Australia is not a sovereign state, so there is that.
Australia is not a sovereign state. Their Governor General is appointed by Queen Elizabeth. The same is true of Canada.
Governor General's Constitutional Duties
-Presiding over the Federal Executive Council
-Facilitating the work of the Commonwealth Parliament and Government
-Dissolving Parliament and issuing writs for a Federal election
-Commissioning the Prime Minister; appointing Ministers and Assistant Ministers; and swearing-in other statutory positions
-Holding and possibly exercising the Reserve Powers.
The Governor General is the Commander-in-Chief of the Australian Defence Force. The Governor-General's duties as Commander-in-Chief include:
-Through Federal Executive Council, appointing the Chief of Defence Force and Service Chiefs
-Commissioning officers in the Navy, Army and Air Force
A sovereign state would not have someone in it that could dissolve their Parliament if a king or queen in a different country wanted it so.