I also don't have time to watch the video, but am somewhat familiar with the topic. One of the primary themes of the dreamtime stories is about the origins of various landforms: how this hill got here, how this valley got there, etc. They're often quite detailed, because explaining the unique quirks of the landscape is part of the appeal. So, not just a generic "why the valley is here" stories, but specific "why the valley has seven sharp zig-zag kinks in it" kind of stories.

There are a number of such stories which tell about landforms which have been under the ocean for 11,000 years, since the great meltwater pulses raised the ocean at the end of the ice age. Long after the stories were documented by anthropologists -- who thought it was unusual that so much mythology would be concerned with the topography of the seafloor -- sonar was invented, which confirmed that the landforms existed more or less exactly as the stories said.

So personally I think that's pretty hard proof of at least 11,000 years of accurate oral tradition.