"Appears to have stayed put" is very interesting. For as long as I remember, the theory was Aboriginal settlement was in waves over a long period of time, from different regions depending on what routes were available at the time (land bridges etc.). Waves of settlement pushed existing populations further south, with the oldest group down in Tasmania (well documented as wiped out by Europeans). Now I'm reading "a single, rapid migration along the east and west coasts", and extrapolating from that the significant racial diversity would be divergence over the last 50,000 years.
Don't have sources at hand, but my impression from news articles over the last decade has been that recent archeological evidence has tended to indicate that aboriginal populations have been in australia for for quite a bit longer than the 50/60K years that was previously believed.
One example: I think there were some campfire remains and associated artifacts in Tasmania that were recently dated and turned out to be a lot older than than expected, like at least 80K years old.
(https://www.nature.com/articles/nature21416 linked from the article)
(A tenancy to stay put might also help explain the amazing density of languages)