Sure ... if you look at my file Test48 you will see that I first created the large cube (Marix) and second the small cube (Core). So when I assign material to the core it references "Box:Solid1" and for the Matrix it references "Box001:Solid1". You can verify this in the Material dialog.
I am now writing a tutorial and recreated the problem, but accidentally started with the small cube (Core), followed by the large cube (Matrix). So the references in the Material dialog are reversed.
Test48 gives the correct results (i.e. based on 2 materials), but the version for the tutorial is incorrect (i.e. based on a single Material).
I therefore presume that in the tutorial case material properties for the Core get overwritten by material prperties of the Matrix.