Note from reporter: This issue has been re-sent by me due to over four months without response. Thank you for reading. I hope it gets read this time.

This occurs in all current versions of Minecraft. When witches are left idle, and wander around randomly, in the process of them walking, they will ignore the player until they have reached their destination, then attack. This can be severely exploited so that you can kill the witch with no effort at all, or more often confuses players into thinking that the witch is a passive mob. This can be seen in multiple YouTube videos.