Summary:
Sneaking will automatically be initiated while stuck in a gap of less than 1.8 blocks.
But during auto-sneaking, block push the player (for example, if the upper half of the slab is pushed into the player). It also doesn't match Java where the player is just sneaking without being pushed.

Steps to reproduce:

1. Build a redstone mechanism that will push the upper half of the slab into the player from above.
2. Set the mechanism in motion so that the player automatically sneaks.

Observed results:
The player is pushed a little while auto-sneaking.

Expected results:
The player is not pushed while auto-sneaking.

Video:
MCPE.mp4