Current numbers in Australian Senate: Government 29, Opposition 27, Crossbench 20, 39 needed for majority. So if the opposition opposes a government bill, the government needs 10 crossbench senators to vote for it - if the Greens support it, that’s enough; if they oppose it, the government can still pass the bill if they get the votes of the 10 non-Green crossbench senators (4 One Nation; 3 independents; 3 single senator minor parties)
I can’t see how this is by any reasonable definition a “rubber stamp”