That sounds exactly like why they said "we've reached a mutually-agreeable compromise." Now neither party will be negatively affected in future business dealings.
> If they don't want people making up their own theories they'll at least say something
Who cares? They have a billion dollars from General Motors. GM itself is a big enough company that opinions on HN don't matter and won't affect the sales of their final product.
They defused a difficult set of complaints in a mutually-agreeable fashion without involving the courts. That's good business. As outsiders, we are not in any involved with them, and probably shouldn't spend any time caring, except to take away one lesson: talk your differences over and reach an amicable agreement. Don't invent drama when none is required!