How about "only Apple earbuds or Apple-approved devices"?
Surely, the point is Apple can easily control what works and what doesn't. Whatever the situation is today is no comfort against the potential abuses of the future.
They have been doing this with headphones for a while now. I became acquainted with this when I had some headphones with play/pause, volume controls, and a mic for my iPhone 4S. After the 4S, I bought an Android phone and was sad to learn the volume controls over the 3.5mm connector were Apple proprietary and the only thing I could do with my $150 Klipsh 'phones as play/pause or answer calls - the volume rocker becoming totally useless.
Surely, the point is Apple can easily control what works and what doesn't. Whatever the situation is today is no comfort against the potential abuses of the future.