We touched on this in a unit I did at uni last year.

Basically, it implies they are all the same - that they all come from the some cultural and societal groups, which is hugely incorrect. The idea of them all being 'one people' (for want of a better phrase) is viewed as being a product of British subjugation and ignorance of the way the nations functioned.

So, it would be like speaking Europeans as a whole race, with no reverence for the fact that "Europeans" are actually German, and French and Polish...etc.

The Koori people prefer to be called Koori, the Bunurong would rather be identified as Bunurong. Like Australian's in general may well prefer to be called Australian's than "Oceanic people".