it’s expected that the Fourth Estate would nonetheless make a show of treating all 13 candidates equally

I don't think that's expected at all. They should be providing a reasonable amount of coverage to all candidates, but that doesn't mean they all get equal airtime. It makes sense that ALP and LNP would receive the most, as the parties most likely to win. Smaller parties with significant political presence like the Greens and One Nation should receive a healthy amount of airtime too, with the more fringe candidates being given an opportunity to present their case fairly, but not necessarily much more than that.

For sure, our media is too biased in favour of the big two and the coverage of the Fadden by-election is a particularly bad example of that. But it's not reasonable to expect them to go so far in the other direction that every candidate gets an equal amount of airtime.