Defenses baits the offense into making a throw, and disguises what they are doing, like if they see that formation they can have the DE/OLB defend that pass. Rex Ryan does this a lot. Anyways, its not a play you have in your bread basket anyways. Teams will prerp for it now, and I doubt we use it anytime soon.
I think you are missing the option aspect of the play. The DE/OLB can try to defend the screen pass all they want but if there is a true option to the play, the QB will just hand the ball off to the running back because the defense have left themselves vulnerable to it. Another option for the defense to consider from that formation is that it may not always be WR screen.