The Guardian piece doesn't sit immediately obviously with the others, although it does talk about how the SFF market is a little more open to Australian - as opposed to British or US authors - than it used to be, which is one kind of diversity. It mainly caught my eye because there has been quite a lot of discussion on the IAFA listserv this weekend about how to decide an author's nationality and if it matters for academic work. My take on the issue is that unless the argument you're making - or question you're asking - is directly to do with nationality, then it's probably either irrelevant or not the best category to be using. And it is central to the argument/question, then you should think - and write - carefully about the ideological implications of using 'nation' as a category are, and about where the labels attached to an authors come from. Who decided that x person - who might be born in one country, raised in another, and having their work published globally - is of y nationality?
Jonathan Strahan, who runs the Coode Street podcast (nominated for a Hugo this year), is quoted in The Guardian article suggesting that Australian SFF is characters who are "alienated from landscapes – they see themselves and the places they come from as being outside the mainstream of events" and the impact of the colonial experience. This is the kind of argument that does make sense out of using nation as a way to group authors together so that you can compare work. The tendency towards alienation from the landscape has been part of non-indigenous Australian culture since colonisation.