I wonder if they mean the 'popular' definition of a catapult (that is, the rock throwing giant spoon like thing) or an actual catapulta (that is, a giant cross-bow that fires a bolt, while the other is actually a ballista because it fires a ball.) These terms got confused during the 1700's because some 'giant crossbows' fired balls.

And yes, a trebuchet is the best ballista ever invented... so much fun!
~CSL