Hyrri's Truth does not affect Precision reservation

I have a character in Standard who is trying to squeeze in the Precision skill using Hyrri's Truth - which should give it 100% increased reservation efficiency.

However, the amulet seems to have no impact at all at Precision's reservation value for my character.



Here's the print showing that the amulet is equipped and that it's the current version of the item.



Here's the print showing how much mana the skill reserves. My character has 31% increased mana reservation efficiency of skills from the passive tree, so the skill reserves less mana than normally. However, it's still reserving far more mana than it should - it's simply not considering the 100% increased reservation efficiency from the amulet.

As a further test, if I socket in a level 19 Precision gem in my gear, which has a base reservation of 176 mana, the game will reserve 134 mana regardless of whether Hyrri's Truth is equipped or not. Equipping the amulet has zero impact on the reserved mana.

I've also tried buying a different amulet to check if the issue was on the item itself, and it made no difference.

EDIT: Also, if I spec out of the reservation efficiency passives on my tree, the level 22 Precision reserves 202 mana - the full value without any reservation efficiency.

EDIT²: Tried equipping the amulet on a different character. Still has no effect on the reservation of the skill. Also tried using a divine orb to update rolls on the item. No change.