The core catalog is really a catalog of Material widgets. This is probably mixing two things.
I think there are two things here:
A) a core set of logical UI elements: check box, radio button, etc. This is not design language specific, these are core logical widgets we should expect to be always available.
B) an "out of the box" implementation of the logical UI elements, which in our case is the "core catalog" of Material widgets
We should consider creating two concepts more clearly. And, we should consider CoreCatalog to be more like a "MaterialCatalog", so it's more obvious what it is. And , if we create the "logical UI elements" concept, then it should be easier for an app to choose their own implementation of those logical UI elements.