So oddly enough, the rattling noise was only present on that cold morning when I made the original post. It has warmed up since then and I couldn't replicate the noise after that day. On my drive to the dealership yesterday I could no longer hear it, not even in stealth mode. I still informed the service advisor about it but the likelihood of the technicians doing anything about it when the issue is no longer present is slim (what the advisor told me). For the record I did go to a different dealership since they were the only ones who could provide me with a loaner car. If it comes back, however, I will take it to the dealership that originally replaced the exhaust since they are more familiar with me and the exhaust defect.
If anyone needs the service bulletin for it here it is:
https://static.nhtsa.gov/odi/tsbs/20...82403-5448.pdf
On my original post I mentioned that I was taking it to the shop for an unrelated issue. This was due to the check engine light coming on. They did look into that and turns out that a "exhaust cam solenoid" went out and will be replaced under warranty. Not sure if that had anything to do with the noise I was hearing or not.