Do you know what else is from Blizzard? These 3 books right here. These books are chocked FULL of retcons and controversial changes that many people questioned when they came out and still do to this day. You say everything that Blizzard says matters, yet as we’ve seen from these books, even Blizzard can’t be trusted since they have a tenancy of changing extremely huge story plots. I’m pretty sure back in bfa they even retconned something from the book as well, so even then, the books can’t be trusted either. Now compare those with a simple tail for worgen. Is that a huge game changer? Nope, it’s not. You have artists and employees in Blizzard right now who are for giving tails for Worgens, it’s only a matter of if or when they will do it at this point.
Also, those tailed worgens in Hearthstone are also directly from Blizzard. 
https://i.imgur.com/iv3ic3P.jpg