Well, three-level grill straps are shown in the US owner's manual and the exploded US schematic. Maybe not just an Australian thing? Or maybe it is an Australian-only feature that has been included by accident in the US documentation and in a few US grills. Apparently Ryan Ung in the US got one.My understanding is that the straps with a middle level were all the Australian manufacture or model. I have a newer (S6) and only has the two levels for charcoal.
An inconsistency I've noticed is that the US manual shows when used in the upper position, the support ring consists of three rings, but when used in the middle position, it consists of only two rings.