Horn variations will not work right now and will always default to the first registered NBT value of instruments
This turned to be a bug and here is the explination from @TPGamesNL (thanks to him for helping in finding this out)
The alias loading has a de-duplication mechanism, AliasesProvider#L295. Because goat horns are new to the API, there's no ItemMeta for it (probs will be in the future). Because of this, the only difference between a ponder goat horn and a sing goat horn (for example), is an unhandledTags thing in the ItemMeta impl from CB (see screenshot). Skript doesn't (isn't able to?) check this, therefore, when comparing the ponder goat horn and sing goat horn for the de-duplication mechanism, it thinks they're equal, so makes them point to the same item.
Some issues were found while testing on MC 1.19 https://pastebin.com/KMMqvNuB
NOTE
Horn variations will not work right now and will always default to the first registered NBT value of
instrumentsThis turned to be a bug and here is the explination from @TPGamesNL (thanks to him for helping in finding this out)