When you summon a witch using this command: "/summon witch ~ ~ ~" and you move one block away from her,where the distance between you and her is 1 block,the witch will start attacking you, but she will not throw correctly her splash potions on you ,the potions will go far away above you without hurting you .

Wanna reproduce?

1-type this command "/summon witch ~ ~ ~"
2-move a little bit from her,until you become contacted to her(like talking with her) and make sure that distance between you and her is 1 block.
3-you will see the resultat that she will not throw correctly her splash potions on you.