Err, no. Even if a guy who is called Justin Steinway (example) would make the retcon it would be official as long as he has the right to do it. That is how the world of money and law works. Own a brand, own the rights. People just say that if they don't like the changes. You have the right to ignore them but that does not make them non-existent when it comes to what is official. Companies have rights, companies decide. Not the fans - except when the company says "it is up to the player". If Square suddenly sells the rights for Final Fantasy VII to other people those peoples' story changes are not canon? That is not how it works. And in case of Final Fantasy VII it is not a problem at all because the most important person for the story is not Hironobu Sakaguchi, but Kazushige Nojima and he still writes the stories.
The company can say whatever the smurf it wants to say, and I'm perfectly free to ignore all of it since it isn't a creation of the entire team that created the original game. Sakaguchi may not have been the main writer but he certainly still made major contributions to the game. Without his involvement, every story development that comes out is not a creation of the entire team that wrote the original story, and thus does not wholly reflect the entire vision of the team that made the original game.

And I'm sorry but I couldn't get through your wall of text in your second paragraph.