If a DB jumps in front of the receiver on 3rd and long, the quarterback cannot throw the quick first down pass, and it gives the pass rushers that extra second or two to get to the quarterback. No, you cannot do this on every down, but you can vary it. If an opponent knows you will give up the first down pass in lieu of the long pass, it will throw the short first down pass until you try to stop it. This is the responsibility of the defensive coordinator. It would be wise to jump in front of the receive at the beginning of the games when they are making their first one or two drives. They then decide to go for the long ball after you have shown that you will not let them have the first down pass. The defense then switches, understanding that the offense will then try to go for the pass over the DB. At that time, however, you have guessed along with them and the DB drops back for a couple of drives.
The old adage: You can fool some of the people part of the time, and you can fool all the people some of the time, but you cannot fool all the people all the time, unless you are Tech's offensive opponent. Football is as much a guessing game as a physical game.