I guess you could also argue Darmstadt doesn't have a watermark
I consider Darmstadt more of a waste of tiles than an expansion. Thematically it doesn't work, the rules are slapped on without much thought, and the visuals are inconsistent with anything else in the game (except arguably The School). The ugly fleurs de lis are just icing on the cake. That being said, I consider the fleurs de lis to be a terribly inept attempt at a watermark, but I suppose they also fall into the category of "otherwise useless symbols on tiles that tell a player that a ruleset is in effect." Although I do own Darmstadt, it is probably my lease favorite expansion so I apologise for pretending it doesn't exist.