Reverse went out

Maybe drain and capture the rear wheel gear oil; verify the measured amount and take the appropriate next steps based on what you find?

It's extremely easy to perform the rear wheel gear oil service.
... or just open the filler plug and shine a light in there ... you would be able to tell if it is 'wet' or dry ... in the worst case stick a wooden skewer stick in there like a dip-stick and see if you get oil ... I know that running these final drives 'dry' they will not live long .. and if you indeed ran it without oil, then there is already damage to the hard-face of the gears ... just my 2¢

Agree with first doing a simple check like Ulrich suggested and if any doubt as to the level I too would drain while saving the contents as Scott Semone said would be prudent.

As a possible wildcard explanation for that obnoxious whining while riding is it possible you are hearing the fuel pump? This was not uncommon on earlier bikes and a software update took care of it. On mine it was often very subtle and at other times it was embarrassingly loud so it may be a case of now that your being more attentive while assessing things you are noticing it? There are some good vids posted on the forum w/audio you could compare with what you're hearing.

Glad you have a helpful shop and this is all sorted quickly.

🍺 🍿
Okay I got another update, the dealer just did the driveshaft relube update and then diag that the “reverser” is faulty electronically. They will need a new module of some sorts that will come 3 weeks from now since there are none in the United States… so riding with no reverse for the next 3 weeks. I was offered extended warranty for 3 years unlimited miles at $1,700. The sales person said it will cover everything like an OEM warranty and this one is from RPM I think. Any thoughts? Bike only has 519 miles on it and my warranty expires Oct 10th. I just got it not to long ago with 89 miles so I’m trying to rack them up but with some assurances..
There is a thread on the forum with the price sheet reference the BMW OEM extended warranty. This provides coverage just like the original new bikes have and IMO vastly better than any aftermarket vendor like RPM. In your case with the bike being so "new" and with so few miles I would spring for it. My bike has been trouble free at two years and 18,000 miles, but I may add the BMW plan before it's next birthday just for the peace of mind and while a bit $$ still very good value given the costs of everything in both parts and spiraling labor.
1600 miles on the TC…while using reverse it simply crapped out. Has anyone else had reverse stop working? Come Tuesday I will be scheduling a service call with my BMW shop.
Did the r light flash mine does this now and again just restart it will work perfectly again