Whatever happens on wallpaper side under the hood on old android versions is so messed up. At some point of using my Android 11 tablet and experiencing a lot of lag when any custom wallpaper was visible on the screen (but not when default one), after lots of digging I discovered that lag was completely gone if I set my wallpaper in portrait orientation. Had to install some separate wallpaper app from google for that but at least lag's gone. Just another little example of weirdness