The nature of political party organization is hugely important here. The majoritarian operation in Australia is vulnerable to backbench spills all the time. If you go to the old Parliament building in Canberra and look at the total number of Prime Ministers of Australia, it's enormous because of the spill system. That's hugely consequential, but it has nothing to do with the electoral formula.
On August 31st, 2016. See this statement in context.