I'm a little drunk right now, but who is talking about a body triangle as a sub? Does that happen in this game? All a body triangle does is control your opponent. It's not a sub technique. I'm confused.
It should be in the game a lot if it sets up a sub or strikes that can't be defended.
While not generally considered an effective sub, it is still a submission. Much like the can-opener is generally seen as a way to pass guard, the body triangle is a may to maintain position, but still can (and has) made people tap out: the Fruit-Bat example cited above is probably the best known case.