He’s a terrible source for everything he’s written about, just so you’re aware anon.
My friend Ciera over in @roottea says that a specific branch (Draconic Wicca) requires initiation after study, but it’s not specialized to a particular demographic of people like Hoodoo and Voodoo/Vodou are; in addition, other forms of dragon magic are open. Given that she’s an actual practitioner, I trust her more than anyone else.
Also, dragons as a concept aren’t closed. There are dragons in all kinds of stories in many variations of limbs or no limbs. Overly Sarcastic Productions actually talks about dragons (from a writer’s perspective) in Red’s episode “Trope Talk: Dragons”. It really shows just how many things we call dragons.