Yeah I think you are correct, it is a system app provided by Sony.
I did notice that Facebook also add this badge to the app icon as well, but I am guessing it to is a some type of system app as well.
I did Google it and found that most devices do it differently, so it's not a Android thing it's really a device thing and like you said there is no reliable way in doing it unless I find the settings for every phone (which is almost impossible and a waste of time).
I think I will just stick to the notification status bar for now.