...and the Border Force's 'final decision' on arrival was challenged and overturned by the Federal Circuit and Family Court of Australia.
Not exactly. Border Force's decision was not challenged, the manner in which it was applied was challenged successfully. Transcripts show they had told NDj they'd give him until 8:30am to contact someone to assist him with his request for a visa but then acted at 7:42 to deny him a visa. It was that action that the judge found to be outside the law and it is for that reason that the Immigration Minister can still revoke Djokovic's visa if he so wishes.