I could see that the leaves are 3-lobed. However as far as I know, the juvenile leaves of neither subspecies of Brachychiton populneus have lobes that are much broader and shorter than these.
Seedlings in Brachychiton populneus (Kurrajong) on 16 Aug 2015 show variation in leaf shape. This one was only about 20cm tall when I found it in 2016 (see Nearby Sightings) but the leaves have not changed much. I think all Brachychiton populneus in this region are subsp. populneus.