Ken, That's what I mean when I am talking about preventing the cut from wandering. Scoring interrupts the grain, lessening its ability to do so. If you study closely the faces of these timbers, you will find the spaces between the marks are not always flush, this is evidence that the grain can indeed still draw the cut to a small degree. However, since it only has 3" to work with it will not cause any problems.
You will also notice in the picture above that some of the faces of the timbers are a lot smoother.
