Actual examples. I can’t think of a case where the package was targeting the public interface; I’m not saying it has never happened, but I can’t think of a single case. In contrast, I can think of lots of cases where packages broke each other. Heck, a couple of us fixed one in just the last 24 hours: remove the hack added in #498 to avoid `InitError` by aviatesk · Pull Request #500 · aviatesk/JET.jl · GitHub.
So again, you’re making a strong claim. Prove it with examples that you’ve checked actually trace back to breakages of Julia’s backwards-compatibility guarantee.