There's nothing ambiguous or misleading, what you're actually objecting to is the
concrete and
specific use of language to describe ideas you don't like and which you don't want to see proliferate. You aren't objecting to people being mislead, you're objecting to people understanding. Do give 1984 a read, I think you'll find the irony that you are appropriating a term used in that book in order to invert it's meaning and to take the very actions that the book is criticizing quite amusing, and then we can be in on the joke together.
Heterosexuality doesn't have to be the default, and indeed, that era is ending. The evidence for it is right here; you feel compelled to go to bat for the notion, not something you'd need to do if it really were mystically natural and inextricably true. Heterosexuality is promulgated as a default because it is key to a power structure called the patriarchy. The patriarchy works by assigning certain gender roles to men and women; these roles allow men to subjugate women, and also allow men to be subjugated by other men. The patriarchy's strength lies in the rigidity of those gender roles, and as the gender roles are loosened the patriarchy gets weaker. Lots of power within our society is expressed through patriarchy, for instance, the idea that men express their agency through violence instead of through emotion and that they should readily throw their lives away in service of a cause is useful for recruiting men as soldiers and police, and soldiers and police are useful in upholding many other power structures (like state power or the power of the rich). So over the last few millenia, many different power structures have come to rely on the existence of patriarchy, and it's been woven into our mythology and the fabric of our society. The fluidity of gender roles is a direct challenge to patriarchy, and people with nonconforming identities have been forced into the closet through violence and social reprisal.
This was a natural series of events in the sense that all of history took place in the context of the natural world, sure. But cancer is natural, we don't have to accept it. In the same way, I reject your heteronormativity. I think it sucks. I don't think people are "naturally" any particular gender, it's a role we learn to play as we're socialized. That doesn't make it bad, there's nothing wrong with being a man or a woman, there's nothing wrong with embracing very traditional views of what that means if that's what makes you happy. I live my life as a pretty traditional man. But that isn't all there is to life, and that's not all it should mean to be human.