The definition is probably an inaccurate one at best.
It might make sense if "modern" man was the first of our species, but we know that is simply not the case.
We have evidence of "homo erectus" and, more significantly, neanderthal man.
Neanderthal goes back at least 250,000 years, and in the case of the migration mentioned in the article, we are only talking about 60K to 75K years.
Neanderthal knew how to fahion weapons, had flint technology, understood how to use fibers to tie and plait reeds, grass, rock (flint) and wood, etc..
They also knew how to fashion animal skins into clothing, specifically, cold weather clothing.
I'm reasonably sure that knowledge was passed down as to what animals provided the best outer wear, having water-repellent qualities, or heat insulating capability.
Homo sapiens was intellectually capable of learning such knowledge from their contact with neanderthal, and adapting it, even expanding upon it.
There is evidence that neanderthal, in turn, learned the idea of personal decoration and symbolism from Homo Sapiens.
You are, however, more than likely correct about the ice travel scenario via Indonesia to Australia, with the exception that the Toba eruption, coinciding with Ice Age conditions may have produced extreme cold snaps for a few years, maybe even a decade or more.
Such a climatic event occurring at the equatorial region would be extremely rare and even improbable, but not impossible. ( just my opinion )
That leaves us with sea travel, which would probably be the more likely scenario.
Migration along the coastal regions would have amply provided opportunity to learn the best ways to navigate the oceans.
Even without sails, fairly long distance travel can be achieved by rowing, if the crew is large enough, the dugout big enough, outriggers are used to stabilize the boat.
As for sails, a quick internet search didn't provide any archeological evidence for "weaving" past approximately 15,000 years ago, but something as simple as a reed mat, or even handmade fishing nets could have been the basis for rudimentary sails.
Simply hanging fishing nets up to dry would have been enough to show how they can catch the wind, and a simple process of net to woven fabric would have been pretty obvious once a "tighter" net was made.
Reed mats would be used as both ground cover and draped over supports for shade.
Any gust of wind would have demonstrated the facility for such mats catching and holding the wind, and if being used for shade on a sea-going vessel, be it raft or dugout, a practical demonstration of use as a sail would have occurred almost immediately.
Problem solved, please notify the archeological community. ;oD
Early 19th century adventurers and explorers give us our information about the "tool kit" available to the nekkid natives in Tasmania.
They were very primitive, as were the nekkid natives in the far South of South America.
Neanderthals were pretty cold adapted ~ hence their size and geometry. Likely those bad boys could go out in a below zero raging gale and treat it like just a breezy day.