Thanks for coming back and naming those puzzles — that helps. Was there a particular moment or choice in 16, 24, 26 or 33 that you liked? No need to replay them; anything you remember, including a part you disliked, is useful.
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.