Witchbane Jewel doesn't work with DoT

Description of Witchbane Unique Jewel says: "When you Kill an Enemy affected by a Non-Aura Hex, become Immune to Curses for remaining Hex Duration". But it doesn't give Curse Immunity if you kill enemy with Damage over Time, with bleed in my particular situation.

A picture with the bug report reference number there is for the rules, but I'm also adding the videos to present the problem better.

Bug report reference number: 3505362400
Image:

Videos:


I have found other bug reports about this but it is not fixed yet and it still in the game for the 1.5 years: https://www.pathofexile.com/forum/view-thread/3334245. Because the bug is not in known bug list I have added it here again.