On the contrary, the second link in the grandparent's post is basically how all distinguished buildings in the center of Paris and Madrid were built at the time - a subtler form of modernism, still with strong classic influence, but Art Nouveau nonetheless. The ones you link are more artistic and emblematic, but that kind of building is much less frequent.

Have in mind that Art Nouveau is a pretty wide and heterogeneous movement, and not all of it is of the "flowery" nature.