I don't think that it is done by Android. I am running on a brand new 'phone with the latest level and cannot reproduce it, and it is not something that I have seen on previous Android levels either.
@sadegh nordeh - I think that you have done something unusual but I cannot guess what it might be. Start a new, empty app and compile it straight to your 'phone without adding any code. Do you still see an icon instead of the "Click" button?
Starting in Android 12, the SplashScreen API lets apps launch with animation, including an into-app motion at launch, a splash screen showing your app icon, and a transition to your app itself. A SplashScreen is a Window and therefore covers an Activity.