@MichaelMulvaney I pulled all these ones out. There were no seeds. But I was concerned that they were in the riparian zone and that they might become established there, where the is more moisture & potential for spreading. I'm not sure if that is significant but it is a quite different type of environment to where other sightings are recorded.
It is a bad weed in the Southern Highlands and does seem to like sandy soils, so I think you are correct to be worried about it and thanks for puling them out .