When stack batching is enabled, NeoForge IItemDecorators are not rendered for those stacks. An example of this is that Mekasuit energy levels from Mekanism are not rendered with batching active (tested on 1.21.1).

I've split this off from #790 as the original issue now has a PR open which fixes it. Fixing this one will unfortunately require reaching into NeoForge internals, as the ItemDecoratorHandler class is not public API, but you need it to determine which stacks have a decorator registered.

Ohhh that explains why the light block state overlay just didn't work..