How certain are you that corner warping no longer works on PC?

I don't recall the exact circumstances, but at one point after picking up the scuba mask I was messing around in that room and got teleported to the room where Claire is almost tortured in a cutscene. It may have been related to climbing over the shelving but I think I was actually swimming around in the water below, to the left rather than to the right where the passkey is.

It seems a very similar effect to the corner warping, so I'm wondering how "fixed" it really is. Also whether this warp to the Claire room is useful in 100% runs :)

The leaderboard suggests that casual and normal are basically the same except Normal skips some cutscenes, but I don't think it's true. I tried a speedrun on Normal and noticed that I often had less than full health, and I consistently died during the final boss battle, about half-way through it.

It wasn't bad up to that point though, so perhaps it's worth starting in Normal and switching to Casual just for the final boss battle, which you can do through the menu.