Oops, sorry for the mis-info and thanks for the correction. I guess I was mixing up our system with bi-xenons.
I think you'll find the moving projector on MB (and Audi, BMW, etc.) is for the purpose of self-leveling the headlight beam which is a requirement for HID lamps in Europe. This is to reduce glare for other drivers when cresting hills, etc. where the beam would otherwise be significantly above the horizon.
HIDs are either "bi-xenon" (both high-beam and low-beam come from a single light source with a shutter to change beam shape) or separate projectors are used for high-beam and low-beam. Unfortunately, some unscrupulous aftermarket vendors call their product "bi-xenon" when they've spliced a halogen high-beam filament onto an HID capsule for use in halogen housings (both illegal and stupid).