Not sure where you heard that.
I like to remind Leafs fans about playing Boston in 1969 (Bobby Orr era). They lost 4 straight, starting off with 10-0 and 7-0 beatings in the Boston Garden.
Not the finals, but still.
Take heart. If you're a numbers person, the home team has gone 15-2 in the last 3 years of the cup finals.