I’ve never understood why this rule is enforced in the General registry, e.g. here. If a package changes in no other way than narrowing supported versions of Julia, that is to say that no new functionality is introduced nor is old functionality is changed, then it seems like Semantic Versioning has very little to say about whether the new version should be a major, minor, or patch version. In fact the SemVer spec has a section about this very case which says that either the minor or the patch version can be changed.
Isn’t it the job of the package manager to figure out whether a package version is compatible with your other packages, and current version of Julia? Why force minor version increments when no new functionality was added?