I think that there should be an expanded x and y. By this I mean that you can make a scrolling game where you can't see the sprites on the ends. I have had to make a sprite that covers these so it wouldn't look bad. I think you should be able to have a sprite that you can not see because it is too far off the screen.

Sprites must remain on-screen unless hidden so that people like New Scratchers don't loose them . Unfortunately, covers are the only option in Scratch. However, in some Scratch mods, namely BYOB, there is a selectable option to allow sprites off screen.