Cryptomatte material differentiation between materials with the same name. As reported already, when materials share the same name, whether or not belonging to different multisub materials, Vray considers them the same material for masking, not sure what happens in compositing software. Unfortunately when working with external assets, people tend to name things like trunk or leafs, which, if you have 50 plants and trees from different sources, can be quite a hassle to rename manually. (VrayCryptoMatte, doesn't work with Xref Materials. - Chaos Forums)
What would happen if the same material is part of two different multisub materials? Should it generate the same Cryptomatte ID or different?