Identifying the mislabeled HMAS Australia model

Why did a Sydney museum label an echelon-turret HMAS Australia model as a heavy cruiser?

The model's echelon turret layout identifies the 1911 battlecruiser, so the heavy-cruiser label appears to be a museum error.

Two major Australian warships carried the name HMAS Australia. The County-class ship was a heavy cruiser, while the 1911 vessel was a battlecruiser. An echelon arrangement for the wing turrets identifies the earlier battlecruiser rather than the County-class cruiser. Since that ship was disposed of after World War I under treaty requirements, a postwar heavy-cruiser classification would be incorrect. The display appears to have confused the two namesakes.