They said you can use both screens as one, but that's not the intended usage. Therefore, the device isn't optimized for singlescreen usage, but dual screen. Two verticas screens horizontally aligned would be suboptimal for their intended use as you'd have vertical screens. Hell, Nintendo wants to encourage using both screens, if they opimized it for usage as one screen they could just as well have made a single screen and called it the GBA 2, but that's NOT what they want.