I think it’s akin to a child growing up with technology, and therefore being able to operate with it at an intuitive level.

These interns have never not used AI (in the industry), so they haven’t had the “handicap” of traditional development experience that slows down their AI usage.

A senior will see a problem they’ve done a thousand times and do it again the same way, a junior with AI will try to make it fit into any new hole they find.

"AI-native" refers to understanding what new areas of value are unlocked by the existence of modern AI systems, and which old problems no longer matter because you can just have Claude trivially deal with them. Not everyone who's familiar with AI tooling necessarily has those instincts.