Great article. I'm a sucker for anything D &D related. I wish I had gotten more into it as a kid, but alas, those days are gone!
To be totally honest, I'd say the writers just drew on what they knew, did a little bit of research and got on with the story. While it may be great for a handful (and by handful, I'm obviously referring to millions of nerds worldwide) of nerds to fixate on some inconsistency, but the show just wasn't about playing D&D. It was about another freakish monstrosity that abducted a kid for reals.
If you're into fantasy writing, I'd love if you'd check out a story I'm writing (part of a larger saga, "Adventures in Elowyn Glade.")
Cheers!
Nick