The Melb. Cup was run on a 'good' track. It was upgraded to good straight after the race. Meaning it didn't suddenly become good after the 7th. race. They always water to avoid a hard track now, but the 3mm of rain that fell that they could never have predicted, added a little more than normal, but it still ended up a good track anyway.
Sour grapes are always around after a Cup, it's just that this time the mouths they came from were bigger than usual and the press made a meal of it.

My bitch is about all the earlier races that where run on an obviously dead track, which would have given unfair advantage to some horses over others from a deliberate act [watering] to suit one race on the card :-)