I might have missed something, but it seems like it was the tournament organizers who made the mistake. They were the ones who told Djokovic that he had a valid

I might have missed something, but it seems like it was the tournament organizers who made the mistake. They were the ones who told Djokovic that he had a valid medical exemption, whereas the government's position is that he does not have a valid exemption. If that's the case, then Djokovic could potentially take the issue up with the tournament organizers, but I don't see why that would mean that he should simply be let into Australia.