If you shift on the edge of the block while walking backwards, it looks like you're standing on the air

The bug

If you shift on the edge of the block while walking backwards, it looks like you're standing on the air.

The old 1.11.2 sneaking behavior was like half of your feet is in the block (two screenshots with inventory shown is the version 1.12 and the one with no inventory on it is 1.11.2).