It eliminates the back shoulder throw - in theory. the trail technique is not meant to be trailed by 2 or more yards though. You are slightly behind the WR hip and if the S is over the top, the window to complete a pass is very small to no window. it's a very good way to play a deep ball. Some of the speedier guys use it as a bait to the QB to have him think the WR is open, then they catch up and make a play on the ball, etc.. several reasons to play the technique, it just was not executed very well in this case.