Straight wall collision box expands when something is above it.

Prior to the 1.13 snapshots, straight walls that connected to only two opposing sides would keep the same  smaller collision box regardless of if there was something placed on top of them or not. Now they expand to match the rendered size. It's possible that this is intended however this also means that if a player is up against it when it expands, they glitch into it a bit if they try to push forward.