I've been working with an Apple support specialist to collect diagnostic information to submit to the engineering staff for investigation. That information was just sent off this afternoon. I have another call scheduled with them tomorrow to confirm receipt of that information and creation of internal trouble ticket. At this point, they acknowledge there is an issue, things are not behaving as they should, and they intend to follow-up. Once created, the trouble ticket has a tracking # that user's experiencing the same problem can reference when calling in.
I did some more testing that confirmed that (for me, anyway) ringer volume is not affected by the hearing aids being turned ON or OFF. But alert tones are, on average, 15 dBA lower when the hearing aids are ON and connected than they are when the hearing aids are OFF. A difference of 10 dBA results in perceived volume to the listener being twice as loud or soft.
I'll post back here when I've talked with Apple support with anything new they have to say.