Eh... If your adversary can break modern bluetooth encryption, I probably... would not bet on this? I would think that with appropriate radio equipment you can probably pick up audio from many wired headphones.

bluetooth encryption has been broken before. "KNOB" (https://www.usenix.org/system/files/sec19-antonioli.pdf) was less than 5 years ago. The kind of equipment that could pick up the audio over a wired headset from across the room could probably pick up something from the speakers of wireless earbuds too.

I wonder if there are attacks based on RF emissions along a cable to get the sound

Yes, there are. You can even get video signals from a video cable.

Not if you have a good microphone and the sound is loud

That's not a failure of the protocol but of the user. It's like saying PGP for email can be broken if you have a telescope to look at the user's screen.