Depending on how one looks at the question, you are absolutely correct. If the question comes down to "How many and what changes have to happen for a product to be given a different name or a different edition number or be considered merely an errata'd update etc. etc... there's no objective standard with which any of us can use. So anyone's feelings on it are merely choices and opinions, including WotC's. I don't disagree with this take.
But the other way one can look at it would be that because WotC owns the product they are changing and that they are the ones who get to make the choices to change it... then they are the ones for whom their answer is by definition correct. They are defining the question and defining the correct answer. We may argue about whether we agree, but their answer correctly satisfied their own question.