Possibly a cultivar of a couch hybrid (very fine stolons and leaves). I know it looks like couch grass and is also called quick grass, twitch grass, etc but I have never seen the common couch grass grow like that from a central point so quickly! I notice it is listed as an native but some authorities consider it was probably a very early introduction.
To quote from the reference on the species page: "Some authors believe that both native and exotic forms of this species are present amongst populations in Australia." See: https://keyserver.lucidcentral.org/weeds/data/media/Html/cynodon_dactylon_var._dactylon.htm