Is there a way to stop it from “updating” my wallpaper? The suggestions I’ve found online don’t address this specific issue head-on--the “updating” wallpaper when I’ve never had any widgets or wallpaper. I’m guessing this is some malicious process from Apple to drain my new battery and there’s nothing I can do about it.

I don’t have a wallpaper set. Never have.
I don’t have widgets installed. Never have.
The lock screen is black, shows only the clock, the flashlight, and the camera button, as it always has.
then you’re going to have to rephrase what you mean by this: