Thanks — by directional cues, do you mean the starting pipe arrangement, or the markings for start, finish and connected pipes? Was the unexpected route what you enjoyed, or did it make the board confusing? One example from any of those puzzles is plenty; no need to replay them.
From what I remember, it's basically because some details change from straight pipes into right-angle bends, which makes the most obvious predicted route incorrect and forces you to take a detour—or else you just can't spot the so-called predicted route at first glance. Personally, I actually enjoy that sense of confusion more.