I believe Apple’s protocol is one way, that is it sends sound to your HA, but if you want to talk you need to talk in to the phone mic. Phonak uses standard bluetooth, which allows 2 way communication, so they can put a mic in the HA and you can leave your phone in your pocket.
I haven’t read up much on the Phonaks. Can you listen to stereo music and talk to your voice assistant at the same time? That’s being touted as new functionality in LE Audio.
@d_Wooluf I just tried listening to Spotify on my Pixel and activating the assistant. The phone automatically pauses the music - this is not an HA or Bluetooth thing, it works as designed. If you’re talking to your assistant, it’s going to silence anything else.
I think it’s a limitation of Bluetooth Classic. You’re trying to enable stereo sound and a voice channel in the other direction on just one connection. With LE Audio, you’ll have three connections that are co-ordinated but independent. You can talk to your voice assistant or talk over the top of the other party you’re talking to on your phone and it won’t affect what you hear at all. I’m happy to be corrected on the Bluetooth Classic thing.
@d_Wooluf Regardless of bluetooth limitations, google assistant silences other audio, whether its bluetooth or using the phone’s speaker. The Marvels stereo with 2 separate streams, one to each ear. For phone connections, it’s 2 way - you can talk over the other party. On android, you’re speaking through a mic in the HA, so it’s via bluetooth in both directions. I believe they use some kind of black magic to do this 
Galaxy a54 5g has BT 5.3
Just to clarify: My post that you responded to is 4 years old. Lots of phones now have BT 5.3. It’s still unclear how well they support LE Audio and Auracast.