Smelter's Wrath Bolster node is not increasing endurance threshold while charging

Bolster: While charging Smelter’s Wrath you have more armor and endurance threshold.
(+75% in both with 5/5 points spent)

The armor part of this works perfectly fine: 5742*1,75*2 ≈ 20096 (base effect already doubles armor while charging)
The endurance threshold part is at the very least not visible.

In the provided video I am gaining a miniscule amount of endurance threshold.
I believe that to be from the Defiance node (+1 ET per 2% uncapped elemental res) in the paladin tree. I did not do any calculations to see if this makes up for the small increase

I thought that maybe the node doesnt work with effects that give endurance threshold based on max health and tried to put on a belt with 150 ET. Still no noticeable difference.

Logs and a video can be found in my drive folder
Full skill trees/passives/equipment are visible from the LEtools build planner
(I havent bothered thinking about which equipment to use pls no judge ty)