Witch's vertical attack is inept

Steps to reproduce

1. Create a creative flat world.
2. /setblock 0 13 0 stone
3. /tp @s 0 14 0
4. /give @s bow
5. /give @s arrow
6. /summon witch 10 4 10
7. /gamemode s
8. Shoot the witch with the bow & arrow.

Expected result

The witch throws potions at you.

Actual result

The witch throws potions at your X, Z location, but only gets them 5 blocks up from the ground.