The story was retold in The Last Testament of Lucky Luciano, claiming close to 100 mafiosi were killed around the same time as Maranzano. Plain bullshit! The myth is a prime example of Mafia sensationalism, the kind used to sell newspapers and books. The story even made The Guinness Book of Records! And it was all lies.
Hairy, I looked it up in the LToLL. Lucky said the story was complete BS. That's where I got the info where Scarpa to was killed. I agree there's inaccuracies in the book, but the Night of Sicilian Vespers is not one of them, iirc.