Projectile facing doesn't match direction of movement

A projectile's facing (for purposes of /tp) does not match the direction it's moving or pointing in.

What I expected to happen was...:
When a player teleports to a projectile, they should be looking in the direction the projectile is moving in.

What actually happened was...:
When a player teleports to a projectile, they are looking in the direction the projectile is moving in, but inverted along the x and z axes.

Steps to Reproduce:
1. Create a new creative world
2. Make sure there are no entities other than yourself in the world, and that none will spawn.
3. Press F3 (Not required, but useful as it displays facing.)
4. Face east, and fire any projectile.
5. While the projectile is in flight, run the command "/tp @p @e[type=!Player]".
6. Notice that although the projectile was fired east, you are now facing west.