It is a consistent outcome, the recent election is an anomaly. The explanation for why this is the case is a bit complicated but the crux is that only one candidate can win in each seat and while we have preferential voting, the preferences only matter in each race -- and if you aren't in the top two on first preferences then you won't win that seat (nor any other seat where that is the case). It would be easily possible for them to have 0% representation, it just so happens that the Greens party leader's electorate is incredibly pro-Green and so he gets ~47% of the first preference vote, which is unusually high and makes him win the seat easily.

Our upper house is far more representative because each state and territory has multiple seats and thus you can get a more representative outcome.