Even if the docs call use vars "superseded", it still has its occasional uses, because the functionality isn't the same as "our" in every respect.

No, that's what Exporter is for.

As long as there's nothing else in the module, where's the benefit?

In this very specific, narrow case, probably not much. But specific, narrow cases have very bad habits of becoming general, larger cases on their own, as well as being physically or mentally cut&pasted into larger cases. So when the cost of doing it "cleanly" is so small (one package line and two Exporter lines), I think it's well worthwhile.