Giving NPC Priests Turn Undead

Last night the party was adventuring in Curse of Strahd.
In the previous session they had acquired the module-specific magic item

and given it to an NPC accompanying them,

In last night’s session the NPC was able to attune to the item, unlocking among its other powers the ability

Bane of the Undead. You can use the icon as a holy symbol while using the Turn Undead or Turn the Unholy feature. If you do so, increase the save DC by 2.

As I understand it, this power can be used only by those who already can Turn Undead. And this particular NPC does not have the Turn the Undead feature. At first I thought this was because he appeared to be a named NPC Acolyte, a 1st level Spellcaster, while PC Clerics don’t get Channel Divinity (Turn the Undead) until second level. So I checked the Priest Stat Block, since another important NPC

uses the Priest Stat Block. I was surprised to find that, as written, the standard Priest NPC does not have the Turn the Undead feature either. Nor does the War Priest NPC in VGtM.

I am, in general, wary of giving NPCs PC abilities, as the game should be focused on the PCs as exceptional individuals. And I don’t think that every NPC Priest needs this ability. However, these particular priests follow the Morninglord (Lathander), a deity who is opposed to undead. And given the setting (Barovia), protecting their congregations from undead is a central part of their ministry. Thus I think it is reasonable to give this particular NPC Priest the ability, as usable by PC Clerics (one use per long or short rest). For the NPC Acolyte, I am considering granting him the ability to Turn Undead by expending a spell slot, as a sort of reverse case of the "Harness Divine Power" found in TCoE.

So, what am I missing? Is granting the ability to NPC Priests and Acolytes to Turn Undead in setting-specific instances unbalanced? Normally unbalanced would mean the new power would justify an increase in their CR but as these are not PC-antagonists here it might mean that the ability will somehow detract from the experience of the players or reduce the challenge to them significantly. Are there any complications I should be aware of? For example something specific to this module that would make this a bad idea. A good answer will provide official examples of other NPCs or monsters who do have this ability, either in standard Stat Blocks or module-specific adjusted ones, if there are any.