I remember reading about this.
http://www.crusades-encyclopedia.com/cannibalism.html
It’s not so much historically verified, but it’s at the least hyperbole on the actual goings on. Old wives’ tales, if you will. Remember, the winners write the history.
The winner? The winner of the First Crusade was the Crusaders - and they wrote about cannibalism during the siege of Antioch.
The winner of the entire Crusades was the Muslims (a couple hundred years later) and they TOO wrote about cannibalism during the siege of Antioch.
When both sides of a conflict agree on a point - it is pretty well historically verified.