About planes and alternate universes

I've seen a lot of people talking about alternate universes, especially after the "It's not easy being breezie" episode. (The episode aired a couple weeks ago, so screw it; we're talking about it.) Now, a lot of people have been calling all the kingdom of the breezies an alternate universe. Now, I really need to get this out of my system:

It is NOT an alternate universe or an alternate world. It is a different, coexisting plane.

Now, most of you avid tabletop RPG players are more than aware of the word "plane". Most of us, however, might remember the "Elemental planes" and some sort of astral worlds. However, these planes of existence sometimes coexist as overlapped planets. In World of Darkness, we had the Umbra, the Spiritual Plane, but we'll go for better known examples: The spirit world from the Soul Reaver games; the Dead Side from Shadow Man and, for an example much more similar to the breezies' home; the Emerald Dream in the Warcraft Universe.

These planes of existence require means to travel between them, and while they both coexist, your presence in one of them doesn't affect the others.

Now, an alternate universe is not something you can get through a portal or anything. To make one of those, you alter something from an existing "universe" (using it as a template) and making everything work from there. My favorite example is Legend of the Five Rings' "A thousand years of Darkness", which is set in the land of Rokugan, but with a minor difference: Fu Leng, the Dark Kami, won the war in the Day of Thunder, and ruled for a thousand years. The world is the same, but a minor detail that changes everything. Come on, guys, you have the same thing here with the "Nightmare Moon defeated Celestia and night lasted forever" or "the Sonic Rainboom didn't happen, so the Mane 6 didn't get their cutie marks" stuff. THAT is an alternate universe. It's still Equestria, so it's the same "universe" (that's why I use quotation marks), but it's different because it was altered by some change. So it's mostly more of a "what if" than a real plane of existence.

And I'm sure most of us will ask me "Hey, what about Equestria Girs?" Well, it is certainly not an alternate universe in the literal term (since, as I mentioned, AUs are more of literary tools than real, existing places), but some sort of non-coexistent plane. Which would be a bit weird because, if that were true, EqG-plane Twilight and Equestria Twilight might have met each other (since Equestria Twilight is a visitor, which doesn't mean that EqG Twilight shouldn't exist, if basically EVERYONE else on the show exists there.) But that's overthinking it a bit. I still have to watch the movie.