Presumably the point is not the specific emphasis on your native tongue exactly, but rather a mastery beyond what might be regularly implied by mastery of a lan

Presumably the point is not the specific emphasis on your native tongue exactly, but rather a mastery beyond what might be regularly implied by mastery of a language (able to converse like a local) and rather mastery unique even among native speakers (able to convey ideas many different ways with a particular glibness that others can easily understand)