ARW14

I have a 2020 GMC Sierra AT4 with 38,000 miles and recently it started making a vibrating noise coming from the rear. I took it into the dealership, and they told me that it's coming from the rear differential and that they all start doing that. They say there is no fix to it. They diagnosed it while sitting in the passenger seat when I took the for a drive. They have found this on other AT4s and told me that's the way it is. Wondering if anyone else is having this issue and if they have found out what it is?