Over the last month, my updates from Apple Support was...drum roll...No update available yet from the Apple Engineering team.
My newest email update was to install 13.3.1 (which I did Feb 2nd) and reset my Cellular Data usage. Currently sitting at 308KB in under 48 hours. A huge difference from my 4GBs in 72 hours in December, but still creeping up.
after doing the update, I have co tasted Apple Support via my email thread with them to ask when they’d like to speak next since doing the update. Waiting on a reply.
I have not installed or uninstalled any apps in about 6 months. From Jan 10th to Feb 2nd, I had used 485MB of data under Uninstalled Apps with no change to my cell phone usage pattern. Some of the suggestions may work for others, but I use some of the suggested apps regular my (ie Wallet). I hope it can work for some, but with no change to my apps, this is a ridiculous amount of time (and data) for Apple to not know what is happening.