Since rotations take time, rotating towards dead ends of the is not only useless, but annoying, since units tend to move slower. This was reported as a bug at rP24415 by @ValihrAnt.
I hate this fix, can at most be a temporary fix. Probably a better fix would be, is to handle obstructed move before they happen: compute short-paths if we expect collisions, instead of when a collision has happened.