The title is editorialised. Path sanitisation has been a consideration for a long time, but the work on it has been slow. It touches many places in the stack, from macros to the build system with workspaces and external registries. On top of that it complicates already fragile debug info.
Making it primarily a privacy/reproducibility issue is stretching it. It's not a rocket science to build in a docker/vm/nix and get similar results.
And even beyond this specific bug, the Rust project has cared about reproducibility for a long time. There’s even a tag for it on the issue tracker.