The seed heads of Dichanthium sericeum usually have 2 branches and sometimes 3. This one seems to have more. Bothriochloa macra seed heads aren't usually "furry" like this specimen. Otherwise it looks like B. macra. Since it is growing with B. macra, I suspect that is what it is.
According to the description in "Grasses of NSW" (Wheeler, Jacobs, Whalley) D. sericeum has 2-4 raceme branches. The plants I looked at had 2, sometimes 3 branches. The stem nodes were also conspicuously bearded, although I see this also is seen in B. macra. Since the plants I saw were growing near to B. macra, I could see they were very different from B. macra.
The specimens of Dichanthium sericeum I have seen were not so robust as yours, with 1 or 2 raceme branches. But I looked at other specimens on the internet and you mentioned bearded nodes. So I decided you were correct after all. When you look at up to 100 sightings a day you sometimes make mistakes!