Just got the call! My battery arrived on precisely the day Hyundai said it would. Knock me over with a feather!
I'm having them inspect and change the oil in the differential and inspect my motor noises at the same time. Surprisingly, he said that they have done a drivetrain replacement at their dealership so are familiar with the issue. He said that the drivetrain issue was isolated to the early builds. When I told him mine rolled off the line in December 2018 I could hear him sigh and say "Oh" in a very sad way.

I'm hoping that means I've got a sympathetic ear. We'll see. Very excited...as I pick myself off the floor!