i dont think berezaa has worked on the variant stats of hats (and boots) yet.
Yesterday I got a Pristine Vest, the lvl. 2 armor, and it had +5% XP on it. I sold it, but still an interesting find. It’s probably just a glitch.
Headwear equipments are the glitch, they are not supposed to have variants yet.
Equipment like body armor or weapons normally have variants unless only obtainable by a shop or a quest.