Comment by benbayard

The difference is that it has the same aspect ratio folded and unfolded. If you look at other folding phones the inside screen is twice the area, but the shape of the phone is different. 1 : sqrt(2) is the only ratio where you can fold one side in half and the ratio stays 1:sqrt(2). Any other ratio of sides and the inside and outside have different ratios. Therefore, things have to move around, or scale.