Wallpaper Dimming / iOS 18 bug?

So far, iOS 18 is running like melted butter and so smooth. It feels more stable and the battery life also feels vastly improved. There's a few things though.

I don't know if this is a big or not, but when I switch my apps to dark mode, my wallpaper also dims as well. Is this how the feature is supposed to work or is this a bug?