It may come down to a difference in what we mean by “layer” in bella, it is not just a simple stacking of another bsdf as it may be in some other system, it is a real simulation of a thin layer of dielectric material over the substrate (whether conductor or dielectric). So its purpose is not really the same as what I think you may have been expecting.
So yes, please play a bit with the blend material and see what you are able to do, and then we can think about possible solutions for simplifying that.