@12344321
It is true that different continent models are recognised not just from country to country but also from person to person, given, as I mentioned, there's always been a lot of disagreement about what constitutes a continent. However, many of the landmasses grouped under Oceania have no real relatedness aside from being islands lying within the same general corner of the world - it is a geographical region created for convenience. In this sense it is understandable why Oceania is utilised as a continent category by Frontier.
The Australian continent (which also has several other names, such as Sahul, to avoid confusion with the country) has actually been widely recognised, especially in scientific circles, since the 1950s, given unlike Oceania it is easily definable and contained as it constitutes a continental shelf. More recently there has been growing awareness that New Zealand, New Caledonia and some other South Pacific islands actually lie upon an enormous sunken mass of continental crust known as Zealandia, far
far larger than any other known microcontinent or continental fragment, and that such a landmass would have been recognised as a distinct continent long ago had 94% of it not been underwater.
I'll link the three relevent wikipedia articles below (note how the Oceania article specifically avoids referring to it as a continent):
https://en.wikipedia.org/wiki/Oceania
https://en.wikipedia.org/wiki/Australia_(continent)
https://en.wikipedia.org/wiki/Zealandia
No? From what I understand countries such as Brazil that reject Australia in favour of Oceania are also more likely to recognise things such as a single America. I personally follow a seven continent model, but one which joins Europe and Asia into Eurasia (my concept of continents is largely based on physical distinctness and biogeographic boundaries, in which case there's no reasons for them to be separate continents) and recognises Zealandia as the 7th continent. Basically, what are commonly referred to as "geological continents".
Despite all this, you're still free to class what you want as a continent really.
Unlike the continent discussion, which is subject to a degree of intepretation, this is simply not true. The Southern Cassowary is much more widespread in New Guinea than it is on mainland Australia, just look at the distribution map below. Not to mention that cassowaries as a whole are, like tree kangaroos, heavily associated with New Guinea despite also occurring on the mainland.