The title of your hypothetical website would be an oxymoron. All the websites like this that I’ve seen are titled as general concepts or concepts that would require more than just a picture to exist. “Fluttershy” isn’t a general concept and would “exist” with only a picture. If your website was specifically for Fluttershys, then a more accurate title would be something like “Now This Fluttershy Exists” or something.
But anyway, I agree that they shouldn’t be tagged as canon characters and think the “not” tags are the best solution.