The thing about training camp is the defense doesn't react like they would in real games because there's no game to lose. They can go all out and jump on throws they normally wouldn't. Plus, they haven't been gashed by 5 yard runs all day so they won't bite on play-action passes etc.
For defenders, they just have to go to the ball. For the offense, the receiver has to run the right route, the QB has to throw the ball to where the receiver is going to be and the offensive line has to open up lanes for the QB to throw in.
There's a big difference between closing on the ball and throwing a ball through a window to a spot on the field that might have a defender already in the vicinity in hopes that your receiver read the defense right and is running the correct route, meanwhile feeling the passrush; not to mention Parcells hovering over you ready to rip you a new one.
Just wait until the real game when if jump a pass and miss, the receiver goes for 6 and you are playing from behind the rest of the game.