Look at the plan for 70 and 80% vaccination.
The modelling they are using says with 70% vaccination and less than optimal TTIQ (i.e. a lot of cases as they are currently experiencing in NSW) to keep the case numbers under control is likely to require:
stringent capacity restrictions,
group size limits,
stay-at-home orders (except work, study, essential purposes)
at least some of the time.
At 80% you are still likely to require
capacity restrictions, as in NSW 23 August 2020
With the NSW case numbers, it looks likely they will require High PHSM (no household visitors, curfew, stay-at-home orders except essential purposes & permitted work) even at 70-80% vaccinated to relieve the load on the health care system. Cases won't go down instantly - it will take weeks.
If you are a state that is currently at zero COVID, the 70 and 80% plans require you to shut down large segments of the economy. You can see why WA is not too keen on that. For a state like Victoria, if we can get back to zero, we can open up more than we can under the national plan. For the 6 months over last summer/autumn, we had much more freedom than we will under the national plan.
The point of the national plan seems to be to open up borders. I like travel as much as anyone else, but it is going to come at a big cost to other segments of the economy. It is reasonable to ask what is the rush vs. an extra couple of months for a more complete vaccine rollout? One motivation might be to start bringing in cheaper overseas workers again.