The original idea was that packages listed in missing-docs are the ones that get inherited from the base UBI image and have some content, such as documentation or translations, stripped out; and packages listed in extra-packages are the ones added on top of the base UBI image specifically for Toolbx containers. The stripped out content was to be restored by reinstalling those packages, followed by installing the extra packages on top.

In practice, the set of packages in the base UBI image is not constant and changes over time.

Currently, if a package that's listed in extra-packages, but not in missing-docs, gets included in the base UBI image, then it will fail the missing files test, because the content stripped out by the base UBI image wouldn't be restored.

Therefore, to avoid such test failures, all the packages listed in extra-packages should also be listed in missing-docs.