I had a service complaining about the root file permissions which changed between Fedora versions [1]. I was never able to figure out what produced the file system image but thanks so this guide I know where to start looking now.
https://web.archive.org/web/20230112002240/https://beefymira...
At least 6 years ago, this was not entirely true: a package happened to build only because, by happy accident, the builder had a dependency installed by something else. Since the dependency was not in its Build-Requires:, the build would fail in COPR, which really used a clean room. A case of being saved by the alphabetic order, I guess?
Maybe they have updated Koji since.