I hardly catch difference between "NESB" and "ESL" definitions: to me, all these students are only from a non-native-English-background. That is why their parents and they naively suppose that local degrees could open them a door out of ethnic ghettos people are de facto fixed into in Australia.

What I really agree with you, their non-Anglo-Celtic background must not be a reason for paying the mates speaking a particular English accent more for supposedly teaching this accent to already enough proficient in English: I witnessed lessons in English to middle-aged native speakers-managers unable read and write native English.