I think my issue is more just with the mindset that it's okay to have one narrow slice of supported versions of everything that are "known to work together" and those are what's in the container and anything outside of those and you're immediately pooched.
This is not hypothetical btw, I've run into real problems around it with libraries like gproto, where tensorflow's bazel build pulls in an exact version that's different from the default one in nixpkgs, and now you get symbol conflicts when something tries to link to the tensorflow c++ API while linking to another component already using the default gproto. I know these problems are solveable with symbol visibility control and whatever, but that stuff is far from universal and hard to get right, especially if the person setting up the build rules for the library doesn't themselves use it in that type of heterogeneous environment (like, everyone at Google just links the same global proto version from the monorepo so it doesn't matter).