It means it was top secret until the day it was announced, so the big opposition party were briefed the day before it was announced and there's been absolutely no public discussion at all.

The cabinet just made a huge strategic choice on their own and gamble on being able to sway the rest of society.

> do you guys hold referenda for big purchase agreements

I assume that's a joke? Not just a "big purchase agreement", but as that ABC article begins, "Australia is embarking on its most significant change of defence and strategic direction in decades", because the US and UK want it, not because Australians want it, I guess. It's a total reversal of a policy that's lasted, well, must be 50 years. We've had a succession of remarkably cretinous Liberal[0] governments since 2013, from whom nothing is that surprising—I keep reading about their dreadful decisions on HN lately. But this is pretty surprising.

[0] i.e. the Liberal Party, in Australia the main party of the right.