Identification of wallaby grasses is challenging and requires good measurements of the different parts of the seed. The seeds in your image appear quite small so this could be R. setaceum.
Thanks very much for your help in identifying this wallaby grass. Background: I have a Bradley Method test plot at Umbagong District Park (Latham) to remove St John's Wort. Most people don't use the Bradley Method as it's seen as inefficient and time consuming. However, people also report that methods they usually use don't work (a joint government-landcare / parkcare survey last year). My experience of the Bradley Method is that this is one method that does work for SJW. The Bradley Method requires you to be able to identify every single plant in the plot as everything non-native is removed, not just SJW. Your ident is therefore very useful, thanks. In case you're interested, Ginninderra Catchment Group has uploaded the case study on SJW removal using the Bradley Method (now being scaled up), including methods and recording documentation, onto its website: https://ginninderralandcare.org.au/weeding-st-johns-wort-at-umbagong-case-study-resources/