The only theory that I have heard so far David is that melbourne's outbreak was far more related to large family and community groups living close together and giving it to each other than Sydney's was. It happened in Sydney but evidently was not as pronounced.If anyone can explain this they might just get a Nobel Prize.
It is very confusing the way that we locked down earlier and harder and yet ended up with more cases.
Sure, NSW got some extra vaccines and managed to get the vaccines out a bit quicker as a result, but the trend of cases versus vaccination percentages do not align between Victoria and NSW.
I'm sure there are plenty in the government and in the health research community trying to work this out too.
The modelling from Burnett has changed a bit with the quicker vaccination so I think that may have a bit to do with relieving the lockdown rules a bit more, but also they would be looking at compliance with the rules and what they think they can get people to do. Not much point having rules which no-one follows, better to have rules which most people will follow. No doubt a difficult balancing act though.
DS
It is a theory only but I know there is a lot of analysis going on