Are you referring to anyone other than French and Hastings?
Although not ideal, the club will have weighed up they think its worth allowing them more time in Australia to rest and recuperate with their family and friends and have some normality versus a couple of extra weeks pre-season training.
Hopefully the bit of pre-season they have missed is fitness based and they have kept themselves fit and they join for the actual preparation.
It is worrying that they are not back yet and you factor in isolation. They're going to get 4 weeks max before thhe first game.