Not necessarily. Mirrors don't always have to mirror. They can be enchanted to do different things. Like, a matching set can let you talk to the person holding the other mirror. My mum's got one that gives fashion advice. You're also supposed to be able to use them for divination, but that's just rubbish. I did see a mirror once that showed your greatest desire in the reflection. So, I guess all that's all to say that, yeah, this sort of thing isn't all that strange. At least where I come from.