Summary:
After the player stops gliding with an elytra, their hitbox doesn't update, which allows them to walk through blocks at head height. When the "Short Sneaking and Crawling" experiment is enabled, the player will walk into the block and start crawling.

Steps to Reproduce:

1. Create a new world
2. Place a block 1 block above the ground
3. Try to walk through the block
4. Equip an elytra and glide with it
5. Try to walk through the block again

Observed Results:
After the player stops gliding with the elytra, they can walk through the block.

Expected Results:
The player shouldn't be able to walk through the block.

Videos:
Experiment disabled:
Minecraft Preview 2023-05-26 10-05-43.mp4
Experiment enabled:
Minecraft Preview 2023-05-26 12-26-14.mp4