The CASA information sheet is quite clear that it is in line with ICAO, and the OP highlighting the 'land in a field' option seems to have overlooked that helicopters are aircraft and quite capable of landing in paddocks, car parks and hotel gardens
Although I do think that declaring an emergency (Mayday) rather than a PAN leads to a diminution of the effectiveness of Mayday calls overall and seems to overlook that a reserve is just that; fuel to rely upon if the planned flight runs into an unexpected delay or increased fuel burn.
From one who came through a system where we kept very, very quiet until the gauge read 12 minutes remaining in a single engine helicopter hovering alongside the carrier 