Not surprising, the Prime Minister proves himself to be a liar. From the article:

The prime minister rejected the suggestion that Djokovic was being singled out, but he acknowledged that other players may be in Australia on the same type of medical exemption. “One of the things the Border Force does is they act on intelligence to direct their attention to potential arrivals,” he said. “When you get people making public statements about what they say they have, and they’re going to do, they draw significant attention to themselves.” Anyone who does that, he said, “whether they’re a celebrity, a politician, a tennis player . . . they can expect to be asked questions more than others before you come.”

Apparently, the definition of singling someone out is not asking that someone more questions because you weren't happy with their public statements.