It is well known racing history that some tracks are harder to win on than others.

It has more to do with track layout than track bias [a different thing].

Cauifield is not much more than a trotting track [329m straight] that they tried [and failed] to fix and Sandown had it's hill. Canterbury is tiny [straight also only just over 300m] and hard to punt on. Ranwick is almost square and is notorious for taking your money too.

Basically size really does matter here. The larger tracks create a more even playing field [Brisbane tracks for instance but the huge race fields have to be avoided].