As the title says:
Advancements, loot tables, resource pack names and world folder names do not require to be lower cased, unlike models, structures, textures, etc.
There are even advancements that have upper/camel case in the name (e.g., the folder buildingBlocks) and wolds are called New World(for single player) and World(for multiplayer) by default.
Expected behavior: all files need to be lower cased like within resource packs.
Files that allow uppercase:
- loot tables
- world folders