That probably would would have been better. Oh well. I don't think people would have still understood it made the mirror into an Unversed. The only way to remedy that would be by sticking some Unversed eyes somewhere or something...
True, I think the audience still needs visual cues to pick up on that stuff (like they did with Riku and Armored Ventus Nightmare in DDD). Hell, slap an Unversed symbol on the back of the mirror's face. But. It's in the journal lol. We got it. We're good.