"During the bench press you have to pull the shoulder blades down and back to create a solid base. If this fails to happen, chances are you won't press in a straight line."
This has been discussed in numerous articles, one stating this "because a straight line is the shortest path", and others stating a more of a j-pattern barpath, which translates more to using different muscle domination through out the lift.
Bottom point is, find what works for you, which tecnique you are stronger with and master that.
I would imagine that this straightline-technique comes more from geared powerlifting peers.