This is what I get in my console:

Which makes zero sense, given the fact that I do the shading correctly:

My shade.base reference is irrelevant, but I promise it's not empty lol

You are shading the incorrect dependency, thats why you are also using the wrong shade pattern. Remove the -plugin from the dependency and then fix the pattern. https://github.com/tr7zw/Item-NBT-API/wiki/Using-Maven#option-2-shading-the-nbt-api-into-your-plugin