I recently had a leak in the passenger side. The drain hose in my passenger side A-pillar was kinked. I straightened it and heard water slosh out...But still had a leak. I noticed my window seal was missing in the same area yours is cracked. I replace the whole upper windshield seal with BMW Part # 51317182004.. That seemed to stop the leak for me.

So, Yes, that cracked seal can be a source of a leak.