The appendix in the Return of the Kings explicitly mentions Olog-hai, making it canon.

Any non-canon additions have to be very necessary.

I completely forgot about that. Thank you for reminding me.

Is there a downvote option? :>

"Troll-folk" isn't a wholly accurate translation. Like the Black Speech term Uruk, it applies to a specific sort of troll. "Uruk" is typically translated as Orc, but it really applies only to the larger, stronger soldier-breed created by Sauron in the late Third Age. Similarly, the Olog-hai are Trolls, but are specifically the special sun-resistant breed that appeared at the very end of the Third Age.

There is an edit that should be made to the Ologs' name in the mod, though. I believe the mob is currently called an "Olog-hai," which is the plural form. It's like if the Elf mob was called an "Elves." Should be cut down to just "Olog."