Yes both should tilt / vent same time. Problem is the rear glass can get stuck open so people disable the rear portion from tilting at all (pretty novel idea). Otherwise replacing the roof cassette I think it is runs in the multi thousand$. I like venting my roof for the novelty of it all but becoming more aware it's a timebomb so avoiding it and just opening the front section instead.

BMW E61 E53 Dual sunroof / moonroof / Panoramic Roof - YouTube