Dunno but in all beta 15 dungeons I've played, a lot of corridors end up as dead ends. If you dig the last square, you reveal a hidden room behind. I know the dungeon generator was changed to allow more room shapes, but it's probably a feature not a bug.
Definitely a bug in my eyes, and one which is prevalent across most of the level generators. I don't know why DarkGod doesn't use a simple ConnectFill algorithm.