I wear Resound Vivia Hearing Aids, and use them with Resound Smart-3D with an iPhone 11 in an environment that includes an older Mac and an Apple Watch and a TV Streamer-2.
My experience is that Notifications of text messages on Apple devices suing the same Apple-ID is Black Magic.
Notification Arrival seems almost arbitrary and capricious. I have not detected any connection with proximity of my Hearing Aids.
To make things worse, I am in a cellar near-dead zone, inside a house of solid masonry construction. I have installed multiple different Wi-FI access points to get adequate Wi-Fi coverage.
My observations:
• if iPhone message notifications are on, I eventually get a notification on my phone, forwarded audibly to my Hearing Aids -- UNLESS Mac messages is running, see below. Sometimes the Mac will produce a notification up to a minute or two before the iPhone notification.
• If Mac Messages.app is open, the notification happens on the Mac, ONLY, and there seem to be NO notifications of incoming messages on ANY other devices.
• If Watch Messages notifications are active, the Watch itself tries to send a pitiful little sound and vibrate, by itself (which I almost always do not perceive, even on strongest settings). And there are NO notifications on any other devices. And No Hearing Aid notification whatsoever.
IF anyone reading this has any more information about the rules of how Message Notifications is SUPPOSED to work, I would love to discuss it, and I expect others would as well.