Ivy Blossom lives Here

I think you're right, both about the writer thing and the selective canon thing. I think selectivity/ignorance of book canon is going to lead to a lot of this kind of misunderstanding, probably. I've never seen the RDJ movie (and don't plan to), but I think that's where some of the confusion might come from, too--I've heard it played a little fast and loose with canon, but those who haven't read the stories might not know that? Canon is going to be a tricksy thing in SH fandom, now.