Motion:[X,Y,Z] tag not affecting Fireballs, SmallFireballs, or WitherSkulls

When attempting to spawn in a Fireball, SmallFireball, or WitherSkull and giving it velocity with the Motion:[X,Y,Z] tag, both types of fireballs immediately despawn, not showing any signs of movement prior to despawning, and WitherSkulls do not despawn, but additionally have no velocity and will simply hover in mid-air, not moving. This has been tested with all three of the above projectiles that will respond to the direction:[X,Y,Z] tag.