There are many software stacks that are not versioned only at the top level, especially in scientific software. As an example: If I tell you I calculated a res

There are many software stacks that are not versioned only at the top level, especially in scientific software. As an example: If I tell you I calculated a result on SciPy 1.1.0, do you know what version of what code is doing the linear algebra? No, because there's no single answer. It depends how SciPy was built and what's installed on the rest of my system. It could be OpenBLAS, ATLAS, MKL... So if there were a bug in, say, a particular version of OpenBLAS, and it manifests itself in SciPy, there's no way to tell whether the bug is present based on the SciPy version.