Yes, some of the new EXPENSIVE MB's like the S Class have a shutter mechanism to provide instant high beam light. With the previous system and the retrofits, the Xenon is low beam only. Since you wouldn't get high beam light for several seconds if you were to use the Xenon without the shutter mechanism.
Dean, I think you missed my point. Higher Wattage bulbs are NOT the answer. It's all in the reflector shape. That's why the Euro lights are so much better. Putting High Wattage bulbs in early US lights just generates a lot of heat that ruins everything in the light and sometimes wiring, switches, etc. The payback for all these headaches is very minimal improvement in your headlights. Euro Headlights with standard bulbs is the best way to go. Been ther, Done that!
Best of luck,