I also had my differential replaced a few months ago on my 2016 Scat Pack. It was making the same noise you described and had the oil changed with no resolve so they replaced it. It's been fine ever since. Good news is you'll have a new rear at 61k :wink3:
The diff is mounted to the chassis in these cars, so any sound is magnified.
Also consider that it is a limited slip and those will make a little noise when turning by design.
I've never driven one of these that didn't make at least a little noise at a certain speed or when turning and I drove many Scats and SRTs before I bought mine.