Yeah, I see that I actually read your OP in another thread and gave you a Thumbs Up! but since that was over 19 days ago and you didn’t bring it up in this thread, I forgot and didn’t make the connection.
I downloaded the Nordic Semiconductor nRF Connect for Mobile app from Google Play that scans for and reveals characteristics of BLE devices. It also has a DEVICE information page for the host device (my Galaxy Note 8). Sure enough, it says that my Galaxy Note 8, now running Android Pie, does not support PHY Coded (longer range) but it does support PHY 2M (higher speed). Interestingly, the nRF app says that the Quattro’s at a hardware level are Bluetooth Core 4.1 devices.
I wonder if the nRF app could just be reading the BT MAC addresses and looking stuff up in a database and not actually querying device characteristics by protocol and perhaps missing any effect of subsequent firmware or software updates to a device?? - probably an answer in nRF app specifications but am too lazy to look it up just right now… (later) - seems like from watching developer video on Google Play that service characteristics are determined by discovery, not database lookup! Cool!
Since my Quattro’s have been presumably been upgraded to be BT 5.0 capable by a firmware update, it’s not clear what’s changed but as cited in the XDA article that you reference in your post Bluetooth 5 features, the only mandatory BT 5.0 feature is PHY 1M, which is also in BT 4.2. PHY 2M is just a recommendation, not a requirement, in the ASHA standard, so when ReSound is saying BT 5.0 is required for their implementation of ASHA, it’s a mystery as to what really is absolutely required for ASHA relative to BLE standards…
“It is strongly recommended that the central and peripheral support 2MB PHY as specified in the BT 5.0 specification.” (maybe ReSound is making PHY 2M effectively a requirement, not optional?! - quote is from 1st para after the System Requirement list for ASHA: Hearing Aid Audio Support Using Bluetooth LE
Just for laughs, I think I’ll go outdoors and test transmission range with a clear line of sight. Indoors with the possibility of reflections and variable barriers across walls is an iffy testing proposition.
Edit_Update: I had asked the ReSound Smart 3D app support folks about any changes in the 3D app or the firmware that might make the BLE connection between phone and HA’s more reliable or longer distance and just got the following terse (but helpful) e-mail reply:
Currently we are working on a solution, so we can get more and faster feedback from users of our apps.
Both the app update and the firmware update did contain some corrections which make the connection more stable. One of them are the pairing into Bluetooth settings, as you have noticed.
Maybe a (much) more stable connection just makes for a longer distance connection (better signal-to-noise ratio?).