The issue (if indeed it is an issue) is that pip doesn’t guarantee any preference, and we don’t really want to start doing so. The principle that any compatible distribution file for version X.Y of package A should be equally usable is important (IMO) - it’s behind things like the resolution algorithm, dependency specifications, etc. Once we start saying that A version X.Y from index I is “better” than A version X.Y from index J, then we add a whole new dimension to the dependency resolution process.