Hello,
I don't have a hearing aid to test but the functionality is present (same firmware .231)
You don't have a Rog 5 yet and you want to buy one!!! you are of course of your choice?, you have well read the Rog 5/5s discussion and the long litany of Wifi/Hotstop HS.
FYI, within 2 days, the Rog 6 will be released, it should follow a big reduction on the rog 5s, already effective on the Asus site but shy, in stores in France it can be found from -15% to -40%
If you buy it second-hand, check that the Wifi is OK, possibly compare Imei box/phone.