Nintendo is so good at game development, they make it look easy. I'm reminded of this Ars Technica review of Mario Galaxy 2
It's much harder to nail a satisfying game mechanicâ€”whether it's in 2D or 3Dâ€”than people understand. Nintendo constantly shows you something amazing and masterfully produced, and just when you've gotten over being amazed at how well it plays, the game throws it away and offers up something else, equally good.
Wow that's really interesting. Especially at the end there when he walks off the top of the screen. ... It makes me wonder if that was a bug/oversight that playtesters never found so it never got fixed.
It's part of the level design. It certainly seems Nintendo designs the control and camera schemes first and then bases level design entirely on those constraints. Notice they use the camera rules for water and a vine to get the camera vertical. Once Mario is back on the ground, there is no need to go back up to complete the level, so the camera doesn't follow him up. Nintendo makes great use of subtle camera cues to guide the player towards the goal.