Personally, if I was going to a place like Melbourne with fog at the field when I left I'd arrive with a LOT more than 30ish minutes. I know a lot of blokes have carried about two hours worth PLUS the diversion when there is fog at destination and other factors not an issue (MLW, MTOW, etc!). This time of year in Melbourne, thats probably not a bad fuel order.
Anyway, I'm not going to cast stones. Maybe it was forecast to lift before they departed and looked like it was going to and then set in again. We all get 'caught' by the weather sometimes (read the six pages on the 737 going to TW a couple of weeks back) and you deal with it and move on.
Regards,