David Levine and I talked about that a bit on the way home. I wondered whether it was used to keep you out of some particularly awful/no-longer-as-mapped vegetation in the area south of the road, which seemed on paper like the obvious place to insert a control in order to force continuous attention to navigation.
From what I could gather, he didn't want to put us out to the north of the road because it would make the course too long (which is what happened last year), and he kind of ran out of steam on course tweaks before the southern option really got any serious consideration. Maybe a desire not to let perfection be the enemy of the good.