Undyed bundles still contain the "filled" predicate which is a decimal between 0 and 1, correlating to the percentage of fullness of the bundle's contents. However, dyed bundles do not have this predicate, meaning that it isn't possible to have model overrides for them based on it.

While this predicate is unused on undyed bundles in vanilla, its behavior is still useful for resource pack creators who wish to add different textures for the bundle depending on the fullness.

Attached is a resource pack that applies different textures to bundles based on this filled predicate, as well as corresponding models for white bundles that should in theory mimic this behavior; however, when using the pack, you can see that this is not the case and that only undyed bundles have this behavior.