Does it work both ways? If a dissatisfied Catholic were to show up at an Anglican church in Perth and say he wanted to join, would he be told “don’t be hasty about this”?
Probably not, but the issue here is not individual conversions. With these new canon law authorizing personal ordinariates, there will be entire parishes converting as a corporate body. The established Anglican churches have lost a lot of people in the last 40 years. Some of these have been parishes. The Episcopal Church has lost a couple of entire dioceses in the past couple of years. I think that sort of move is what the established church in Australia is worried about.
If the established churches want to keep their Anglo-Catholics parishes, they will now have to give them more consideration.