The new Enchantment enums break the Enchants flag for /pic. I had a sign that used all pic flags for a custom item price and the sign would accept any item of the same material type when it was supposed to only accept the custom item. After I disabled the Enchants pic flag, everything works completely as normal again. I'm pretty confident it's related to the new Enchant enum names because I experienced similar issues when updating my personal plugins to 1.21.
Server version I'm running on: 1.21.10 Paper.