I really hate it when people confuse the terms “Canon”, “Headcanon” and “Alternate Universe”.
“Canon”: Something that has been outright been stated in canon outside of a joke, in a way that unambiguously means this exact thing and nothing else.
“Headcanon”: It was never unambiguously specified in canon, but I interpret this on my own in a way that goes along with canon without contradicting it.
“Alternate Universe”: My game, my rules.
They are not interchangeable terms.