I’m not an expert on religious clothing, but the Wikipedia article is pretty clear that it is strongly connected to Islam.

Your comparison is flawed, because while “christian” -> “probably wears pants” is true, the opposite is not. If I tell you I saw someone wearing pants, you would not think about their religion. They could be Hindi, Atheist, etc. But if I tell you I saw a girl in a full body dress, you’d be able to tell their religion pretty accurately.
Also, we are talking about France. If the Abaya is “what they tyipcally wear in that part of the world” then “all Europeans wear pants” is a contradiction.