I completely understand where you're coming from, but I don't like
Idris for a girl because it's "unique". I legitimately like this name for a girl. I also love the name
River for a girl, not to be unique, but because I really do love the name. You can't make assumptions about one person based on something that you think is happening. Could it be that people who first used
Morgan and
Ashley on girls just loved the names?
I'm not usually one for male names on girls. There are only a few exceptions, and all of them are because there were female characters with the names on TV shows or movies. But I am all for people using names they love, and that's all that really matters.