Speaking about getting your panties in a knot, you shouldn't go all period on me, this is still a repost and from what I knew, those were kind of disliked. And still I offered a link and reported this post but not one moderator bothered of deleting this post.
Actually the avatar can be characterized by only water-bending for their ability to learn other element bendings depend on their original ability... water harder to learn fire, fire harder to learn water, wind harder to learn earth and earth harder to learn water.
So yes, the new avatar is a water bender, not just of water tribe origin