The bug
When exiting a boat that is against a wall the player is pushed below the wall if there is a gap underneath it. This doesn't happen in version 1.16.5 but does in 21w13a and later.
How to reproduce
Recreate the setup shown in
Place a boat on the wooden surface in the left of the setup
Enter the boat
Row the boat over to the wall
Exit the boat
Observed behavior
The player is placed under the wall.
Expected behavior
The player would be placed to the side of the boat rather than under the wall.
This doesn't happen in 1.16.5 because of [MC-200195]