You Cannot Be Hindered Corrupt Implicit - Not Working?

Patch 3.28.
Corrupt Implicit - Ghastly Eye Jewel "You Cannot be Hindered."
Jewel is socketed into my character's skill tree, and not a Stygian or gear piece, for reference.

Boss Arena - Hive Colony
Specific enemy -- It That Was Tul

Once both hit 40% health, It That Was Tul begins channeling the tentacle shield during the immune storm phase. Even with the Hinder immune implicit, my movement speed drops into the negatives if the channeled tentacle skill.

Along with visibly being slowed, the movement speed mod on my character sheet verified 29% down to -21% movement speed.

It that was Tul does not apply hinder debuff.

there are alot of similar debuffs. That jewel implicit only stops hinder, not all the similar ones.

I would understand that, however if you look at the debuff from the channeled tentacle shield specifically says "You are hindered" in the top-left.

This is the main reason I've posted, as it isn't shown as a Maim or any other type of slow. It shows the hand grabbing foot icon with "Hinder" specifically in the wording.