Yes, it is true. That's a scene in The Godfather Epic where Don Vito says to Tom: "Does this man have balls?", which was edited in that and the from the Godfather Trilogy on DVD. For further proof, check out Harlan Lebo's "Legacy" book and you'll see a picture where Duvall is holding a card for Brando to read, and another one where Brando is taping the card behind a wall.