I think you read the statistics wrong.
The Leafs are the favourites to win Game 5, there's no way the favourites would have a 28.5% chance. I'm not sure what statistics you're looking at, but there's no way it's 28.5% for only Game 5, maybe for the series.
I was reading the statistic that teams that go down 0-3 in the series are 22-54 in game 5 (assuming they force one), historically.