If it violates Apple's views on acceptable privacy practices, why are they approving the app? They already have guidelines against identifying information or collecting more data than absolutely required. The developer data use page is quite frank about the expectations:

    Apps on the app store are held to a high standard for privacy, security, and content because nothing is more important than maintaining users' trust. 

If a particular app only demonstrates this undesirable behavior when the phone is paired with a particular subset of headphones (or other hardware), then Apple may never notice it in App Review.