I'm positive this is related to SuperDuper. I get the same "Background Items Added" notification ever since I updated to Ventura and updated to the current version of SuperDuper! (3.7.5). In fact, I now receive two such notifications, one from SuperDuper! and the other from Bruce Lacey.
Here's an excerpt from the ShirtPocket blog from Dave Nanian (owner of ShirtPocket, which makes SuperDuper!), dated Dec 16, 2022:
"A recent Ventura release has also started notifying people about "Startup Items" that were installed. Of course, as you might expect, when you set up a schedule, we have to install some items to get those schedules to, you know, run and stuff.
So, Ventura starts telling you that it happened. But - rather than use the Application name, it used the "Development Team Name"...and so people who see that "Bruce Lacey" had added some startup items...confusing everyone. (Bruce, as you'll see in the About box, is my partner in this endeavor)."
iMacM1, Ventura 13.4