Basically Android will change its UI coloring to align with your background image, and 3rd parties get access to knowledge about your designated UI colors, right? I get how that can be a privacy concern.
What happens if you set your wallpaper to automatically change every other hour or so? Does android allow that?
I’m sure, but if you have a specific set of colors matching a specific picture on your phone that nobody else has, I imagine that would be more easily traceable than if it were automatically switched out every once in a while. Granted, the other aspects you mentioned might be enough to just render the effort redundant anyway.