The point of situational football in this case is to catch the QB in a situation to where what they expect, doesn't happen; which essentially gets him to hold the ball a half/sec long. It is not intended to suggest that a DT cover an eligible receiver for a full game/play..it's more of responsible for 'getting to that area'. Also, if you're blitzing LBs/S, better believe that one, if not both, backs will stay to pick up that blitz.
Fairley is out by the way.
And btw, it's a very effective zone blitz…ask around to some of the coaches in your area. I've done in when I coached. I also hated to pick up blitzes when I played..preferred to go out in a route..