Obviously, those odds were calculated back in November. Until the draw is out, all of this is just conjecture.
Not only is Alcaraz out now, but Kyrgios hasn't played a match this year because of an ankle injury and Sinner hurt his hip in the match against Korda yesterday. Plus, Nadal has gone 0-2 in his two warm-up matches. FAA lost in the first round of his first tournament to a qualifier.
The only Slam winners that seem to be in decent form at the moment are Djoker and Medvedev, who play each other in Adelaide tonight. In the United Cup, Tiafoe is 4-0 and Fritz, Berrettini, and Tsitsipas seem to be playing well... but they'd need to play better to win the Australian...