Minecraft Version: 1.20.1
Quilt Loader Version: 0.21.2
Mod Version: 1.4.4

When looking at an item's tooltip, the nbt data gets modified.
If in creative mode, the nbt data really gets modified, but in survival mode, it just looks modified, but isn't really. Using the item will reveal the true NBT stat in survival.
Examples:
When looking at a loaded crossbow, it gets unloaded.
When looking at a hammer from Banilla Hammers the durability gets drained quickly, even going to negatives.

I have verified this issue, I'll update once I know more.

I have fixed this issue in Iceberg version 1.1.18. Enjoy :)