When I first saw the 28mm unit, I wondered why they changed the lens cap design. It is actually an improvement but I still could not understand why this particular design until I had the one accessory for this unit. The LH1 lens hood looks cool attached and the rationale for the lens cap design becomes evident. Pretty ingenious and the bonus it can be used on the 50mm.
However it is not cheap to look cool, I got the hood for SGD 32 and not altogether sure if it makes a real difference to photos.