The transparency mode enabled after running through headphone accommodation customization is going to work for modestly-ish hearing impaired. I was really surprised how well I could hear the air filter running in the next room.
Live listen is something I haven’t used. But I can see a use for it even for non hearing impaired.
I didn't need a study to tell me. I got original AirPods Pro early, and was aware of improved hearing minutes into ownership so that would be few years ago now!
I would like to think that in the future I will be able to buy air buds which will help my aging ears as well as sounding really good when listening to music. I suffer from that irritating condition that makes hearing someone speaking difficult if there is a lot of background noise. A pair of airbuds that was built with this in mind would be helpful.