I believe they could offer the feature and not face the ire of the EU by "simply" documenting the software interface used by the hardware so that third parties can also try and implement it.
Of course then they wouldn't get the ecosystem lock-in they want. In theory. But I know plenty of people who buy Airpods "because" they're "the best", without ecosystem integration considerations.
A big part of why they're considered the best is features like moving seamlessly between iPhone and mac within seconds of starting audio playback.
It's not as simple as documentation. If you document the interface, you need to keep it somewhat stable and backwards compatible.
But if it is internal, then you control both ends of the API, and can change them in tandem.