Walking sideways through a bookcase, crack in the wall, crevasse, is often to mask a load screen, as you suspect. I forget who coined it, but someone online observed that these are literally “load-bearing walls”, and I’ve been calling them that ever since. In the case of Assassin’s Creed, there used to be sort of a puzzle of “how do I get from here to there with only those observable handholds?” Perhaps that eroded over time as the series went on. The last one I finished was Unity, and I sampled Odyssey, but that wasn’t a very vertical climbing game. Assassin’s Creed came from Prince of Persia and Splinter Cell roots, one of which retains that traversal puzzle, and the other is a stealth game, where you have to get from one place to other either without touching the ground or without being in the light. I would argue Hitman’s ledge-climbing fits the same bill that stealth games always have, so it’s not out of place there. I can’t speak to Sekiro or Jedi.