I see I should have elaborated a bit more on what happened before the landings near Darwin.
In TTL, the Ming dynasty never existed. The Yuan broke up a bit earlier and China was divided between Shun (north) and Wu (south), while Shun the most powerful militarily. Faced by a more powerful and expansionist neighbor, guarded only by the Yangtze river, the Wu were forced to become better seafarers and traders, so that they could recruit potential allies and money sources from abroad. An example of this trend is that the Wu capital was at Guangzhou, both well situated to participate in trade with southeast Asia and India, and really far away from the Shun border.
Eighty years pass, and the Wu invite Timur's successor, Shah Rukh, to invade Shun China. He does, eventually succeeding after a long and difficult campaign aided by what was essentially a Chinese fifth column. Except then he doesn't leave, declaring himself the First Emperor of the Tieh dynasty. The Tieh then proceed to overrun Mongolia, Korea, and finally Wu over the next several years.
The Wu are forced to flee into exile. First they go to Tondo, but are expelled when the Tieh demonstrate they have naval capabilities. They then go to Champa, but are also expelled when Champa becomes a Tieh vassal. They then move on to Majapahit, which doesn't want them either because of old trade rivalries, but also bars the Wu from traveling west. With no other choice, the Wu are forced to stop at the first piece of land they come across, Australia. That's the 100 year backstory to the opening post. Hopes that clears things up.
And on the subject of Chinese colonies, I was referring to the 'bunch of settlers pack up and settle in some, relatively uninhabited place far, far away' a la New England.