I agree this would be useful. Also, coming from early versions (VW3 having only 1 prefix per area), this would be the accustomed behavior in many cases, making the current behavior a regression. (After moving to VW4, those areas suddenly have a different default prefix selection when making new articles, because the migration process allows all prefixes automatically).
Since this can be treated as a minor regression, it can be handled as a bug and resolved in a minor upcoming release.