Handsfree calls while streaming audio out over bluetooth to hearing aids

One of my friends has Oticon hearing aids. He streams the audio to his hearing aids after pairing them to his iPhone 14. When he makes a call, he has to hold his phone close to his mouth in order for me to hear him. During long phone calls, this becomes very tiring. He cannot put his phone down otherwise I don't hear him. I wonder if there is a way to make the iPhone microphone behave the same as it does when you put a call on loud speaker while he is streaming the audio out to his hearing aids. Without hearing aids, during a call on loud speaker, I can be like 6-8 feet away from my phone and my friend hears me. It seem the my iPhone amplifies the sound it picks up so that it can be sent on the call and heard by the far end, even if my phone is say 3 feet away. Is there a way to get this same microphone behaviour when he is streaming to his hearing aids so that he can put his phone down instead of keeping it 3 inches from his mouth?